One afternoon in May 2017 Alexander Zverev, a 20-year-old German tennis player with a mane of strawberry-blond hair, walked onto court in Rome to play in the final of the Italian Open. The odds were against him. His opponent was Novak Djokovic, who is the nearest thing that tennis has ever had to a cyborg – a player who can hit for hours with unnerving exactitude, who never gets tired and who has the ability to bend and stretch himself hydraulically to reach impossibly distant balls. The gulf in experience was significant. The Italian Open is one of the Masters 1000 tournaments, the most prestigious events on the tennis calendar after the four grand slams. Zverev had never competed in a final at this level. Djokovic had played in 44.

Alongside Roger Federer, Rafael Nadal and Andy Murray, Djokovic is part of the greatest generation of champions tennis has ever seen. They have been dominant for nearly 15 years, winning 53 out of the 63 grand slams held since 2003. No previous cohort of stars has stayed at the top for so long. But though Federer basks in a glorious Indian summer and Nadal has overcome injuries that looked career ruining, the world knows that they are closer to retirement than the peak of their powers. Victory in Rome would make Zverev the youngest player to win a Masters title since Djokovic won in Miami in 2007. It would also propel him into the top ten, something no other 20-year-old has managed since 2008. And it would confirm him as heir-apparent.

The day was bright but blustery, and as the wind swirled around the steep sides of the stadium it picked up the dry clay covering the court and filled the air with a pinkish haze. Zverev seemed unperturbed. Receiving Djokovic’s serve in the opening game, he applied himself aggressively, hitting hard, flat and deep, rushing Djokovic across the baseline. Before anyone knew it, he was up 15-40. Hoping to arrest Zverev’s progress, Djokovic spun a serve out wide to drag his opponent towards the advertising hoardings. Zverev was alert to it, moving early and hitting it on the rise cross-court. The ball’s pace and line-dusting accuracy took Djokovic by surprise and forced him to lunge with a deep, heaving groan. He got barely half a racket to it, and the ball trickled pathetically into the net. Zverev, his hair restrained by an orange headband, three gold chains round his neck glinting in the sunshine, loped to the chair with a languid swagger.

Zverev is not always so calm. He has been known to charge towards an umpire whom he disagrees with yelling “You fucking moron!” and to smash up a racket before stamping on its sorry remains just to make sure. Then again, he has also embraced linesmen, pecked ball girls on the cheek and joshed with spectators. But that afternoon in Rome he was quiet and concentrated. When it was his turn to serve, he walked to the baseline looking placidly at the crowd, bounced the ball four times and tossed. Zverev’s service action is long and slow: when his knees bend low, his head leans back and his throwing arm reaches into the air with fingers splayed, he looks like one of the distended figures in an El Greco painting.

The speed of Zverev’s serve, which can be upwards of 220kph, is severe but unsurprising. At 6’6” (1.98 metres), he is one of the game’s giants, and has all the long-levered advantages that height brings on a tennis court. But to beat Djokovic you have to do more than serve well. Arguably the best returner in history, he can dispatch even the fastest deliveries with a nonchalant swipe, at which point you’d better be prepared to slug it out from the baseline. Zverev likes nothing more. Having served, he generally rallies from a position deep behind the baseline, where he takes enormous swings and controls points with his groundstrokes. He hits off both wings with equal ferocity but it’s his backhand that does the real damage. A flawless double-hander, it is already widely regarded as the best in the world.

At 3-2 in the first set, Zverev was down 15-30 on his serve. Djokovic looked on the verge of breaking back. But midway through the rally, Zverev launched an assault on Djokovic’s backhand, pushing him deeper and deeper behind the baseline. With his opponent now on the defensive he changed tack and finessed a gentle drop-shot over the net. It spun sideways, died on the clay and left Djokovic standing. Zverev followed it with a wide first serve that leapt away from his opponent, and then another unreturnable one. He was now leading 4-2 and Djokovic had no way back in the first set. “This guy has greatness written all over him,” said one TV commentator.

Greatness is not necessarily what you’d expect if you looked at Zverev. Among the more striking statistics in men’s tennis – a sport which we like to think of as being dominated by the tall – is the fact that no player of Zverev’s height has ever been world number one. Of the 128 grand slams played between 1985 and 2017, only three were won by someone over 6’5”. After a certain point the advantages that extra inches offer on serve are counterbalanced by disadvantages returning and rallying, when long limbs and lumbering strides make it difficult to generate the darting movements necessary for a great return game and the speed required to compete in rallies against shorter, more nimble athletes. The last four men to reach the summit of the game – Federer (6’1”), Nadal (6’1”), Djokovic (6’2”) and Andy Murray (6’3”) – have all occupied a narrow physical range where power, speed and agility are present in equal measure. “History has not been kind to tall players,” says Mark Petchey, a former pro who used to coach Murray. “But Zverev seems different, if I’m honest. The balance he has, the movement he has, it looks stress free.”

Early in the second set, Djokovic tried to take control by running Zverev from corner to corner in an attempt to knock him off balance. Having served wide to Zverev’s forehand, Djokovic then pulled him to the other side of the court, before repeating the pattern, like a man trying to wear out an indefatigable dog. On clay courts players slide into wide balls, leading with an outstretched foot. They move their weight forward through the shot at the same time as they travel sideways. Most behemoths hate situations like this – they’re all limbs and no idea – but Zverev glided gleefully, his heels emitting little sprays of red dirt.

For a while he was happy to defend, hitting slow, looping balls that gave him time to come to a halt, shift his weight and dash in the opposite direction. But then he changed the pace in an instant, unleashing a backhand heavy with top spin deep into the corner. It landed slightly behind Djokovic, who was forced into reverse. With his weight going backwards all he could manage was a weak return, which landed mid-court, bounced high and got slapped away for a winner. “We have seen Djokovic turn guys into pretzels during rallies like that,” one TV commentator remarked. Who was the pretzel now?

As the game wore on, Djokovic’s robotic countenance cracked. At the baseline between points, he began yelling Serbian obscenities, spittle flying. He was annoyed by the breeze, annoyed by bad bounces, annoyed by the apparent conspiracy between his ball and the net. Leading 2-1 in the second set, all Zverev had to do was hold serve and he’d be the champion.

At 5-3 Djokovic was serving to stay in the match. A few minutes later the scores were tied at deuce. Djokovic’s first serve struck the top of the net, looped up high and went out. He turned to a ball boy, smiled and nodded phlegmatically. On match point, Zverev swayed from side to side with his top lip curled into a faint snarl. The ball was fired down to his forehand, and he leapt to his right to return, then shuffled into position for his next shot. But he didn’t need to: Djokovic’s backhand sailed a foot long. Standing at the back of the court Zverev looked up into the sun and raised his arms in joy and disbelief. Embracing Djokovic at the net, he sunk his head into his opponent’s shoulder and kissed it.

One cool evening in April, Zverev was practising at the Monte Carlo Country Club, in preparation for the Monte Carlo Masters, the first big clay-court tournament of the 2018 season. The club overlooks the Mediterranean. You can see yachts sailing by and, on the headland, a white mansion that used to belong to Karl Lagerfeld. Since he was 18, Zverev has lived down the road, in a building where his older brother Mischa, another professional tennis player, and his parents Alexander and Irina, also have apartments.

Tennis is full of stories of family dysfunction – Mike Agassi bawling out the infant Andre as he forced him to play; Mary Pierce taking out a restraining order against the father who menaced her to excellence. But the Zverevs present a remarkably harmonious picture, travelling together to tournaments in a style that is both globe-trotting and endearingly domestic. They even take the family dog, a dark-grey poodle called Lovik who has a Louis Vuitton dog carrier and often gets his own tournament pass. “Everyone in the team has their own job,” Mischa says. “Mum is taking care of the mum things, Lovik is making sure Sascha is in a good mood when he wakes up, because when you see your dog you’re not going to be in a bad mood. Dad’s the coach. I’m sometimes there if I feel like he needs help, other times I’m just a brother. What do you call it? A household? A factory?”

Zverev is compulsive about practice. He has been known to hit balls until well after midnight at tournaments, and at Saddlebrook, the Florida resort where he spends the off-season, floodlights are being installed especially for him so he can carry on training after dark. Today the production line focused on quality control. After an ascendant 2017, during which he’d also beaten Roger Federer in the final of the Canadian Open and risen to world number three, Zverev had started the season horribly. He played indifferently in Rotterdam, Acapulco and Indian Wells, and though he made the final in Miami, his performances were scrappy and error-strewn. His forehand was the big problem – he had lost range and consistency – and that evening in Monte Carlo he was working to get it back. At one end of the court Jez Green, Zverev’s bald, burly physical trainer, fed him balls, which he struck metronomically for minutes on end. Each stroke elicited a rough little grunt, until a ball jumped up higher than expected and he dumped it in the net, at which point the grunt became a long sigh of despair. Patrolling quietly behind him was his father, who has coached him since he was a boy. A tubby man with a teddy-bearish face, Zverev Sr mimed minute adjustments to his son’s swing and muttered suggestions.

Midway through the session, Zverev’s mother, who has shoulder-length, greying hair and was wearing a pink and grey T -shirt, sat down in the bleachers with Lovik on her knee. As the dog dozed, she began offering her own snatches of advice. “Sash!” she whispered, trying to get her husband’s attention using a diminutive for Alexander, “Sash!” Her son was hitting too flat, she thought, and needed more top-spin. Her husband widened his eyes playfully and gestured for her to come down to the court if she thought she could do better. Eventually, with her son resting by the umpire’s chair, she walked on to court and handed him the dog. While he nuzzled the animal, she rootled around in his bag and picked out a fresh T -shirt.

Alexander and Irina were both born in Sochi on Russia’s Black Sea coast, he in 1960, she in 1967. A resort city, it thronged with tourists in the summer months, who packed the promenade, paddled about in pedalos and hiked in the nearby hills. But for Alexander and Irina, there was just one problem: there were no indoor tennis courts.

Both were fanatical players, and to keep their edge they needed year-long practice. Eventually they moved to the capital, and quickly became fixtures of the national tennis team, training at CSKA Moscow, the sports club run by the Russian military that was affectionately known as the Red Army Club. Irina, who reached a top ranking of number four in the country, was known for the beauty of her one-handed backhand; Alexander, who reached number one, for his physical grace and strategic nous.

Compared with everyone else, life for sports professionals in the Soviet Union was good: they had celebrity and a decent salary; they were at the head of the queue for apartments and cars. But their careers were constrained. The government’s sports committee decided who played where, and took all the prize money. Alexander and Irina were rarely allowed to play matches abroad. Alexander’s comrades on the national team thought he had the potential to be one of the best players of his era. As it was his world ranking never climbed above 175.

When the Soviet Union collapsed, the couple was free to roam, and in 1990 Irina went to Germany to play in a tournament, with Alexander as her coach. Someone offered them jobs at his tennis club. They said no, but the following year he asked again. “We thought, why not? We’ll try it for a year,” Alexander says. And so, in the early Nineties, they began working at the Uhlenhorster Hockey Club in Hamburg’s leafy northern suburbs, living in a one-room apartment with Mischa, who was four when they arrived, and coaching all hours. One year turned into two, and two turned into ten. Eventually they became German citizens.

Alexander, whom everyone calls Sascha, was born in 1997 and grew up breathing tennis. Not only were his parents at the club every day, but his older brother, who had been put through a rigorous training regime by his father, was on the way to becoming the best junior in Germany. Sascha watched Mischa compete in junior tournaments all over the world; other players, with names such as Novak Djokovic and Rafael Nadal, would sometimes entertain him. “Novak and Rafa I have known since I was four years old,” he says. “They actually tell me the first time they met me, because I can’t remember. They say, ‘Oh, I remember that junior tournament in Italy. We played, like, mini tennis with you.’” He met Roger Federer at the age of five. “Sascha has shown me a photograph of us together at the Hamburg Masters,” Federer says, “so of course I tell him I remember this moment vividly, because he was such a cute, lovely boy.” Zverev asked for his autograph, and was surprised when Federer answered in German; he didn’t know Swiss people spoke German. “So I got his autograph and he said, ‘Well, maybe if you work hard, one day we might play against each other somewhere.’” With all the confidence of youth Zverev replied, “Yeah, maybe.”

His parents were enthusiastic boosters. Mischa was on a German junior team coached by Boris Becker, a former world number one and three-time Wimbledon champion. “I first saw Sascha when he was five years old,” Becker says, “and the parents said, ‘Look, Mischa is good, but Sascha is going to be amazing.’” Their hunch was based partly on his natural facility – “When you have kids, you can see what they can do with balls!” Irina says – and partly on his desperate competitiveness. Every summer he and Mischa would set up a little net in the garden of their home in Hamburg, and play their own version of Wimbledon, marking out lines with whatever they could get their hands on, from stray bits of rope to wiring from old garden machinery. These matches would run on indefinitely. “He would not understand or accept that he was losing,” Mischa says. If Sascha lost they would have to play again. Mischa would often throw the match on purpose just so he could go to bed.

The two children were very different. Mischa was quiet and Sascha was boisterous. Whereas Mischa occupied the tennis court with a Stakhanovite sense of purpose, Sascha played hockey and football with the same frenetic energy, and trained less rigorously than his brother. “Tennis for him was like toys,” his mother says. His natural gifts carried him far against local competition. But global opponents were harder. When he was about 12, his parents took him to Florida to play in a prestigious junior tournament and he lost in the second round to a younger player. “Afterwards he cried”, his mother says, “and said, ‘I’m the best! Why did I lose?’ And I said, ‘Sascha, you lost because you don’t do any fitness, because you don’t practise enough.’” He gave up hockey, he gave up football. From now on it was just tennis.

In his younger years, when his father was often away with Mischa, he played with his mother. Sessions with her had a relaxed atmosphere. Now he began to train with his father, who would sometimes patrol the backcourt with a stop-watch in his hand, timing sets of cross-court forehands or down-the-line backhands. “He had a very Soviet way of doing physical training sessions,” Zverev says. “We would go to the track and we would run 15 laps, and we had to run them in under 30 minutes. Then we would do sprint drills and 400-metre runs, and then sometimes at the end of the sessions we would have to re-do the 15 laps, again in under 30 minutes. I didn’t like them. But I’d seen my brother doing it, so I thought this was normal, I thought this was something that everybody was doing.”

On the court, his father instilled in him a philosophy of “fast tennis” – sprinting, hitting the ball hard and taking risks in order to win points as quickly as possible. But unlike Mischa, who even as a kid was strong and stocky and hardly ever missed, Sascha was weak and gangly and missed all the time. “It wasn’t obvious that he was going to be better than Mischa,” says Lars Kirschner, who played on the club team in Hamburg when the boys were growing up. “He made a lot of errors. We sometimes wondered whether this was the right strategy.” His nemesis as a junior was an American called Stefan Koslov. “A lot of kids win by not missing, by running and just putting the ball in and making the other kids go nuts with it,” Zverev says. Koslov was that kind of player and he beat Sascha repeatedly.

But to his parents, winning wasn’t important. What mattered was learning to play like a pro. Each time he lost, his father consoled him. “I said, it’s OK , this is not a big problem. We must stay this way, we must practice fast tennis, aggressive tennis. If you lose today it’s no big deal. You must think about the future.”

One muggy night in 2012, after Zverev had lost in the second round of the Orange Bowl, a junior tournament in Plantation, Florida, his father and brother had dinner in Miami with Patricio Apey, a sports agent with form in finding young players with talent: he had once signed a teenage Andy Murray. Over terrible food at an all-American steakhouse, Apey offered to represent Sascha. “I met him in the car park afterwards,” said Apey, a diminutive man, “and I looked up and I went, ‘Holy shit! If tennis doesn’t work out, we’re going to Abercrombie and Fitch.’ Here was this beach-bum kid who was just beautiful!”

The following July at Wimbledon, Apey asked Jez Green, Murray’s physical trainer, to watch Zverev in the junior tournament. Green didn’t watch for long, but he liked what he saw. “He was so tall and gangly, any kind of power meant he was all over the place. But when he got in the right position, with a bit of imagination, you realised that these shots could be something very special.” Green asked Murray, who would go on to win Wimbledon that year, if he could moonlight for Zverev, and Murray agreed. “Sascha was a 16-year-old kid,” Green says. “He was no threat.”

They began working together the following winter at Saddlebrook. At first Green just watched Zverev train. “I realised that to go to the next few levels, they were going to have to change quite a bit,” he says. He sat Zverev and his parents down and explained what needed to be done. “I said, look, what do you want to have a go at? If you’ve really got aspirations for the top five and beyond, then you’re going to need a physique that never breaks down.” That would mean completely remodelling Sascha’s body. The process, he told them, would take five years.

One of the most noticeable recent trends in men’s tennis has been the players’ increased longevity. Between 1995 and 2018, the average age of a pro in the top 100 increased from 24 to almost 29, as fewer and fewer youngsters broke into the top levels of the game. The days when a teenager could arrive on tour and win a grand slam, as Boris Becker did as a 17-year-old at Wimbledon in 1985, are long gone. “Physicality has a lot to do with it,” says Todd Ellenbecker, the tour’s chief physio. “You just don’t have 16- or 17-year-old males able to compete with mature adults on tour.”

The physical challenges of tennis have changed in recent years. This is largely thanks to developments in string technology. In the late 1990s, players started to use “poly strings” made out of tough industrial polymers previously deployed in the aerospace industry. Poly strings have several advantages over the natural gut strings and their synthetic variants which players had been using for decades. The most significant is that they impart outrageous amounts of top-spin to a tennis ball. While gut strings shift in the string bed when struck by the ball, and then stay in their new position, poly strings move and then snap back, giving the ball extra whip. Andre Agassi used to hit forehands at 1,800rpm. Today Rafael Nadal can manage as much as 5,000rpm.

Top-spin makes the ball dip sharply into the court, giving players extra control, and because they had to worry less about hitting the ball out, they could focus more on hitting it hard. “Fifteen or 20 years ago you needed to be more precise,” says Mark Kovacs, an expert in the biomechanics of tennis. “Now you can be aggressive from nearly anywhere on the court. You can really throw your whole body into it.” This in turn made it easier to play from the back of the court: serves could be returned with greater power and sharply angled passing shots could be hit with a greater chance of success. The serve-and-volley style, in which a big server rushes the net to put away a predictably weak return, died out, leaving the sport dominated by players who can outmanoeuvre their opponents from the baseline in battles of booming groundstrokes and lightning foot speed.

All of this created a new kind of physiological challenge. The fitness regimes of players of an earlier generation consisted of lifting weights, running and cycling for miles on end. Players still do all of that, but they have added dedicated forms of training aimed at withstanding the rigours of the new style. Paradoxically, these are not so much focused on making the body move faster, but on teaching it how to slow down. “Tennis is really about deceleration at the highest level,” Jez Green says.

Slowing down has two elements. One is about training the muscles used to decelerate the racket after the ball has been struck. Owing to the force with which players now swing, this has become more difficult. A common injury in the modern game is to the rotator cuff, the group of muscles at the back of the shoulder that extend during serves and forehands and then have to contract to prevent the shoulder being ripped out of its socket by the force of the swing. These muscles break down from stress and overuse, and in the modern game’s long baseline battles they are used more than ever.

Players also need to train the muscles used to stop the whole body when it changes direction on the run – which, because tennis is now more kinetic, it has to do more often. Green once analysed a match between Andy Murray and Novak Djokovic, and found that during a single point they changed direction 40 times. “Train that!” he says. “They’re not stopping easily. They’re stopping with huge force. At some point they’re decelerating 12 times their body weight. Twelve times! And they have to stabilise that and then reaccelerate somewhere else. That force is really ridiculous.” If players don’t learn to stop efficiently, they will not only be slower around the court but, thanks to the forces shooting through their extremities, injuries to their knees and ankles will force them into early retirement. This risk is especially pronounced among tall players like Zverev, because heavier bodies exert more momentum on the run and long limbs are more prone to instability.

The process of reconstructing Zverev’s body required sacrifices. Green requested long training blocks, which meant Zverev had to abandon the tour before the end of the season, missing out on ranking points and prize money. He also demanded that during those two-month periods Zverev play no tennis, otherwise bad habits would come back and render the whole exercise useless. One day, during the first year, Zverev’s racket sponsor, Head, delivered some new equipment for him to try out, and he and his father couldn’t resist. “Jez lost it,” Apey says. “He went up to the father and said, ‘When it’s time for fitness, you listen to me. When it’s time for tennis, I listen to you!’ Then he chucked everyone off the court.”

For almost a year, Green focused on nothing but stability. “The first task with a body like that is to protect it,” he says. He went through every joint in Zverev’s body, making sure it was aligned and then strengthening the muscles controlling its function. This work consisted of a series of minute, slow movements that looked like tai chi. Zverev, who was used to his father’s more strenuous methods, thought it was absurd. “The first sessions were weird,” he says. Zverev lay on the floor and Green got him to do tiny exercises, like moving his leg up and down repeatedly. “I was, like, this is pointless! I don’t think Murray won Wimbledon like this!” Zverev says.

Once Green was happy that each joint was set, he began to direct force through them. He wasn’t interested in strength for its own sake, he was interested in it only in so far as it served a purpose on a tennis court. At the heart of this was a kind of choreographic training to ingrain what Green calls “the tennis dance” in Zverev’s muscles. They would spend hours running through the step sequences that he would employ in every match: the three lunging steps that would take him to a wide forehand, or the five that would allow him to hit a passing shot on the run before pivoting on his inside foot and planting his outside foot to decelerate and shift direction. As well as lifting weights, Zverev would strengthen these postures with squats, which look like the split step every sequence begins with, and lunges, which mirror the deceleration step taken on the run, often attached to long elastic bands whose resistance built muscle control.

At the end of each cycle, Zverev had put on several kilos of muscle – Green aimed for 4kg a year. He then realised that he no longer knew how to play. “I had no idea what was going on in my body,” he says. Suddenly shots that he had refined through years of repetition felt weird and needed adaptation.

Gradually he found a new rhythm and the benefits began to show. “He started to become less wobbly,” Green says. “He started to absorb power, so when someone hit hard he could hit the ball back and everything locked into place.” Players back at the club in Hamburg who’d once been able to hold their own against Zverev suddenly found they couldn’t touch him.

In June 2014, in the first round of a tournament in Braunschweig, Zverev beat his compatriot Tobias Kamke in straight sets – the first time he had ever defeated a player in the top 100. A week later, playing in his first ever ATP Tour tournament, he reached the semi-finals in Hamburg. Along the way, he beat Mikhail Youzney, a top-20 player. “I had no idea I could do it,” he says. “I was in a dream, I didn’t know what was happening.”

As he got stronger and faster, he continued to move up the rankings. In 2015 he went from 136 in the world to 83, becoming the youngest player in the top 100. In 2016 he climbed higher still and began facing the toughest opposition. At Indian Wells, a Masters tournament in California, he came within match point of defeating Rafael Nadal in the fourth round. Nadal saved the point and went on to win the match. Zverev left the court in tears.

He made up for it in June that year. In the semi-finals of the pre-Wimbledon grass-court tournament in Halle, Germany, he beat Roger Federer in three sets. He was the first teenager to beat Federer since Andy Murray did so in 2006.

One afternoon in January, during the Australian Open, Federer was at his hotel in Melbourne watching the tennis on TV . On the screen was the third-round match between Zverev and Hyeon Chung, a 21-year-old South Korean. The match had see-sawed and after more than three hours it had entered a fifth set, at which point Zverev began to implode: he lost his opening service game to love, and before long was down 0-3. He threw his racket to the ground, clamped it with his foot, and snapped it in half. Fifteen minutes later he lost 0-6. He had won only five points in the entire set.

Despite Zverev’s speedy rise, doubts lingered about his game. He had never made the quarter-final, or even beaten a top-50 player, at a grand slam. Matches in most professional tournaments are best of three sets, but the four Grand Slams are best of five. Longer matches sap players’ energy and offer more opportunities for dramatic reversal, and in these Zverev had a habit of collapsing disastrously. The loss to Chung, a player ranked more than 50 places below him, was the most egregious example yet. Perhaps it was physical exhaustion, perhaps it was the pressure of expectation, perhaps both.

After the match Federer saw Zverev sitting on a bench in the locker room. “I thought that I would maybe share a little anecdote from my career,” Federer says. He reminded Zverev that even though he’d won more Grand Slams than any player in history, it had taken a long time for him to break through. “I was also known for maybe being the talent that was never going to fully utilise my potential,” Federer says. He suggested Zverev set himself more reachable goals in the biggest tournaments, aim for a quarter-final first, and not dig himself into a hole. Zverev was only 20, after all; Federer hadn’t reached his first quarter-final until the age of 22. “I thought it would maybe be a mood-changer,” Federer says, “because he was sitting there depressed and I just felt sorry for him.”

Five months later, Zverev arrived in Paris to play in the French Open, the second grand slam of the season. He was feeling defiant. After Monte Carlo, where he’d reached the semi-finals, he’d won the tournaments in Munich and Madrid. Such was his dominance in Spain that he’d become the first player in history to win the event without facing a single break point all week. He had won 14 matches on the bounce, and had amassed more ranking points than any other player in 2018. “Everybody was saying what a horrible start to the year it was,” he reflected coolly. “I guess it wasn’t that horrible.”

The French Open proved a partial answer to his critics. Having breezed through the first round, he got into trouble against his next three opponents, and each match went to five sets. But he found a way to win them all, beating two top-50 players along the way and leaping the hurdle that Federer had put in his path in January, making his first grand-slam quarter-final. The results suggested that he was learning how to cope with the emotional and physical exertions of long matches. But then, a month later in the third round at Wimbledon, he fell apart in the fifth set against a qualifier ranked 138, citing illness and exhaustion. A worrying pattern of vulnerability seemed to be emerging.

Right now, this inconsistency stands between him and the summit of the sport. The two players ahead of him are looking back with interest. “He needs to be a bit patient, he needs success at the grand-slam level where most points lie, he needs to stay injury free,” Federer says. “When you’re as tall as him that’s always going to be a challenge...But it looks like Sascha is working in the right way.” Asked recently about Zverev’s future, Nadal said that it’s impossible to be that good and not succeed at grand slams. If his prediction didn’t come true, “you can come back to me and tell me, ‘You don’t know anything about tennis.’”■

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