Early afternoon in mid-September on the main youth-team pitch at Chelsea’s Cobham training ground, just behind the academy building, and Leroy Sané senses an opportunity. The German is clad in the colours of Schalke, his team level and in the ascendancy half an hour into a Uefa Youth League group game, as he collects from a marauding left-back, cuts back inside Charlie Colkett and prepares to spit away a shot from just inside the penalty area. What happens over the next 15 seconds had Michael Ballack, on a rare visit to old haunts, gawping in amazement.

Ruben Loftus-Cheek, loitering at Sané’s back, forces his body between opponent and ball, takes a touch to shield it from another rival, then bursts between two more panicked markers and away. Sven Köhler’s attempt to block is batted aside. Paul Stieber, dragged in-field, is bypassed with ease now that the Chelsea midfielder has built up a head of steam. Others might have over‑elaborated given the run has taken out more than half the opposition but, instead, there is a pass played calmly to Charly Musonda on the flank. One cross and a Dominic Solanke finish later, Chelsea were in front.

Ballack, from his vantage point in the small stand, apparently turned to his entourage to exclaim: “Who the hell is that kid?” He should probably have known given Loftus‑Cheek, who will make his first World Cup start against Panama in Nizhny Novgorod on Sunday, has been earning rave reviews at Chelsea since the age of eight. At the academy in Cobham, the England midfielder’s progress to Russia is a source of huge pride. The 22-year-old has long been considered the great hope of a polished youth system, the one who would finally make a mark with the club at senior level. Hearing himself consistently described as such convinced him not to seek first-team football on loan elsewhere in the belief his chance was close, and, with opportunities rarely forthcoming, arguably stymied his development.

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All it took was eight games as a starter on a season-long stay at Crystal Palace to prompt Gareth Southgate, for whom he had scored three goals in four games as the under-21s claimed the Toulon Tournament in 2016, to call up Loftus-Cheek to the senior squad. The positive impression made in his debut against Germany in November was enough to convince the management he would be an asset at the World Cup. A 10-minute cameo against Tunisia last Monday and Dele Alli’s strained thigh have now thrust him into the side.

“My goal simply was to have an impact, to try to make a contribution and help the team win,” he said. “I wasn’t thinking: ‘I want to play well so I start the next game.’ But every kid’s dream is to play in the World Cup. Watching at home with your parents when you’re 10 years old, you never think you’ll be there in the future. Even just to get on for 10 minutes … you don’t realise out on the pitch but, afterwards, you take it all in. I’m delighted and, whatever’s next, I feel ready.”

No one doubts that, not least because his journey to this point, from Sunday morning football with Springfield FC via Chelsea’s development school in Catford, has been far from straightforward. A player of relatively average height as a child grew rapidly in his teens, “gaining all this muscle and my bones couldn’t cope”, enduring spells of fatigue and dizziness that, at times, left him fretting over whether his body would handle the sport. At 14 he missed almost an entire season with glandular fever, but there were constant niggling injuries too, hampering progress, stoking the self-doubt.

The back problems still occasionally flare up even now, with Loftus-Cheek, 6ft 4in and 14st, following a strict fitness programme that relies heavily on yoga.

The ability showcased against Schalke, all fearsome power, deceptive pace but wonderfully soft feet, still marked him out and, once he grew into his body, opportunity beckoned. At 16, there had been the distraction of a high-profile dispute between prospective agents over his signature before the signing of a lucrative professional deal at Stamford Bridge, with mind‑boggling figures divulged and debated in the public domain. It took a close-knit family to ensure the problem did not become more disruptive but Loftus-Cheek’s potential made deflecting interest from clubs such as Manchester City and Barcelona a priority. Chelsea paid to keep him from their clutches.

Facebook Twitter Pinterest Ruben Loftus-Cheek controls the ball during a Champions League game against Sporting in 2014. Photograph: Glyn Kirk/AFP/Getty Images

Not that the opportunities followed. José Mourinho had first met him when Loftus-Cheek was in the under-9s, as published on the player’s Instagram account, and recognised his lavish talent. The youngster’s physicality marked him out as a Mourinho-style player and, three months after that burst of pace and power against Schalke’s youth team, he was training regularly with the seniors and selected in the match-day squad for a Champions League group match against Sporting Lisbon in December 2014.

Mourinho, by then in his second spell at the club, nominated the youngster to conduct the pre-match press conference, something he dealt with admirably. The teenager had been thrust on to a pedestal, the whole occasion dressed up as a celebration of the academy, only for the manager to offer the player seven minutes at the end of a dead rubber the following night. He would play one minute of senior football up to his full debut, once the title had already been secured, in mid-May. The anticlimax of it all was palpable.

The manager was not done. A lacklustre 27-minute display in a post-season friendly against Sydney FC in front of 83,598 at the ANZ Stadium a few weeks later was branded unacceptable by Mourinho. The public dressing-down was brutal. “Ruben was saying he had a pain in his back but what I was feeling was that he only had this pain when Sydney had the ball,” he said. “So, with Ruben, it’s one step back in terms of my relationship with him. If he doesn’t know what it means to play for me and Chelsea, it’s one step back.

“Ruben has to learn that, at 19, you have to run three times as much as the other guys and you have to play to your limits. You don’t have to play like a superstar with the ball at your feet because this is not the under-18s. That competition is too easy for him. He’s too good for it, but I don’t accept that a player, when we don’t have the ball, doesn’t press, doesn’t have intensity and is waiting for other people to recover the ball. I don’t accept that of superstars, so why should I accept it in a 19-year‑old kid? He has to learn what it takes to play for us.”

The tactic was presumably designed to drive the youngster on but Loftus-Cheek would play eight minutes in the Premier League as Mourinho’s tenure unravelled spectacularly in the autumn. “Mourinho held him back,” Loftus‑Cheek’s father, Trevor Loftus, said last year. “Everyone behind the scenes was asking: ‘Why isn’t he playing?’ If Ruben was playing for Mauricio Pochettino, he’d have 70, 80, 90 first-team appearances by now.”

There would be six substitute appearances in the title winning campaign under Antonio Conte, who saw raw quality but had tried using him as a second striker behind Diego Costa in pre-season – hardly ideal for a midfielder who had never played with his back to goal – and no role at all in his 3-4-3.

He learned from his senior teammates in training, as he had since being partnered as a 14-year-old with Didier Drogba in a one‑on‑one drill, but, as a member of the first-team squad, he played next to no under-23s football, which left him starved of game-time. Then, last summer, Crystal Palace came calling.

At Selhurst Park, Loftus-Cheek toughened up. That year on loan provided him with life experience at senior level, from how to cope with being dropped or substituted, to adapting psychologically to setbacks on the pitch. He did not experience a win until his 10th match at the club, by which time he had already graduated into the England senior setup. He benefited from Roy Hodgson’s coaching at Beckenham but it was the game-time he had craved and from which he truly gained.

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The youngster was a sponge, soaking up knowledge from the coaching staff and the knack of streetwise football from his teammates, over the course of a campaign that resulted in 24 Premier League appearances, a tally that would have been more impressive had he not suffered that three-month mid‑season hiatus with ankle trouble. “He doesn’t have any weaknesses,” said Hodgson. “He has all the qualities – pace, power, touch, awareness – that you need in a central midfielder.”

He discovered how to win with a team that was not challenging for silverware and learned first-hand the uglier aspects – opponents’ kicks, on-field goading or attempts to unsettle – of the senior game. Contrast his initial outings, when he offered flashes of his quality, with the consistent excellence delivered over his past six starts.

He bullied opponents in that run-in as the team sprinted into mid-table. Palace’s coaching staff marvelled at how “cold” he was in training, particularly with finishing that has only occasionally been glimpsed on the competitive stage. “Since I was a young kid, I have always been calm on the ball,” he said. “That comes down to awareness as well. When you have good awareness and you know what’s going on around you, you don’t need to panic. There is no point. It just makes things worse. You have to stay calm, cool and collected.”

He will return to Chelsea far more mentally resilient and with a World Cup finals under his belt. Loftus‑Cheek spent his day off touring St Petersburg’s Hermitage museum of art and culture with four teammates, but his focus was already fixing upon Panama. The tyro who barged through Schalke all those years ago, leaving Sané in his wake, has a dream to realise in Russia.