A science question to begin -- what contains very little mass but occupies a very large space? Answer: on the periodic table, it's hydrogen, the lightest and smallest element that makes up 75% of the universe.

In Indian football, Sunil Chhetri.

India's most capped player has his sport at his feet and also holds its centre together. In his 18 years in competitive football, Chhetri has moved from being the "next Bhaichung" to carving out his own identity, travelling through clubs in Bengal (Mohun Bagan, East Bengal), Punjab (JCT FC), Goa (Dempo, Churchill Brothers) and, two overseas stints (MLS and the Portuguese league), before his longest run, at Bengaluru FC -- five years, 105 caps and counting. He is today wingman-striker, the goalscorer defending corners, a slight 1.7m humanoid leaping into headers against giants and, after nearly two decades on the pitch, still owning a face that could pass off as teenage imp.

Chhetri's place in Indian football comes from impressive numbers -- 65 goals from 104 international appearances (the highest among current international players), 120 from 247 club appearances around the country, including 48 in 105 appearances over five seasons for Bengaluru FC. Or as Sukhwinder "Sukhi" Singh, who coached Chhetri at JCT and junior India, describes him, "Every era has its star... Sunil is that star of these times."

Chhetri's own hero, Bhaichung Bhutia, believes that Chhetri is a change agent for the millennium, the ideal bridge between two Indian footballing generations. The switch from semi-professionalism of the early Bhutia era -- where by Bhutia's reckoning 90 per cent of players held office jobs -- and to Indian football's new century, when the same amount are full pros, has been given due heft by Chhetri's career. Chhetri had, he says, "to make sure he comes in and does it [professionalism] well to take it further and better and that's what he has done. If a player like Sunil did not succeed and make it big, I think that professionalism and that attitude would really not have carried forward."

At 34, his frame whittled down to F1 driver or tallish race-jockey proportions, Chhetri has become both axis and centrifugal force of Indian football.

Former JCT coach Sukhwinder Singh says every era has its star and Chhetri is that star of these times. AP Photo/Rafiq Maqbool

You have to change games

The Indian team is hours away from their opening match at the Asian Cup, the premier continental competition, after a gap of eight years, where Chhetri will have to be the team's legs, lungs, brain and heart. India's FIFA ranking may have moved up into the 100s for the first time (last count: No. 97), but no one is dreaming grand dreams here. When the next Asian Cup comes around in 2023, India's captain will be 37 and who knows where he and his team will be. Chhetri is in fact the lone frontline survivor from India's last Asian Cup campaign in 2011, with the uncapped 18-year-old Gurpreet Singh Sandhu as AIFF junior pick also a part of coach Bob Houghton's squad. Chhetri scored two of India's three goals in that tournament and since then has remained vital, relevant and pivotal to the cause of whichever team he turns up for.

Talk to anyone about Chhetri and his football and very little comes back at you that is about talent or skill. Yes, he has the Touch -- that innate contact that runs from ball to boot to brain and back in a nanosecond -- ball control, efficiency off both feet and the spring of muscle strength in the air. What marks Chhetri out in his community is reinvention, growth and a thick coat of professionalism.

Renedy Singh, his senior at Mohun Bagan, JCT and India, says, "Touch is inborn, but if you don't work hard to polish it, it gets dirty again." Chhetri has burnished parts of his game to such a degree that his former India roommate, midfielder Steven Dias is astounded. Dias, just gone 35, plays Mumbai league these days, and sees Chhetri going full tilt "for 90 minutes with the younger boys when you don't even realise he is that age. He is that fit, I don't know how he does it." (If it helps, sweets have been banished from the Chhetri diet for at least six years, with only the most minuscule exceptions like his sister's wedding.)

Sukhwinder says, "It's not like he is just a big name playing anyhow. He is playing physically."

BFC, where Chhetri is "captain, leader, legend", may be the reason his career has been made malleable and extended both tactically and physically, with high-quality coaching and backroom support. Yet Chhetri counts JCT, and the quietude of its training bases in Phagwara and Hoshiarpur between 2005 and 2008, as "the foundation of probably who I have become now." With nothing to do but "train, eat, sleep", JCT was far removed from the noisy passion rising out of Calcutta football.

play 3:07 'I took it out and threw it on myself' What did Sunil Chhetri do with his first salary? Who is his favourite footballer? ESPN India puts him on the spot.

It was there that the "next big thing", "is going to be a star ... or not" said goodbye to the 17-year-old signed on by Mohun Bagan in 2002. From JCT, Chhetri wanted to become a player "who is reliable, not somebody who just does a cameo, scores a goal here or there. Now you have to change games. If you want to become big, you have to change games." The club gave him 48 caps in three years (21 goals), notice around the country, an India place and a place where he felt 'like family'.

Like a potato

Ten years after leaving JCT, Chhetri is India's Mr Football, his game recalibrated and expanded at BFC. It began with coach Ashley Westwood, who put him on the left wing, away from his favoured place, front and centre. "The dynamic changes [on the wing]," Chhetri explains. "It means coming back and defending very deep... initially I used to do so reluctantly, I didn't want to. It used to be, 'Why should I?' The game script is rewritten beyond going upfront and scoring goals. It's also going back and defending for your team... as much happiness you get as to score, the same happiness you get when that last tackle comes in and saves a goal." Chhetri finished that season (2013-14) as top scorer with 14 goals.

The move from Westwood's brand -- backed by hard physical conditioning of the kind never seen before in Indian club football -- to the Barcelona school methods of Albert Roca and Carles Cuadrat has meant having to absorb failures in order to make positional play part of muscle memory. "We had worked on it for so long, small work every day and you think nothing is changing, nothing is moving, and suddenly the whole wall moves..." Chhetri is animated describing BFC's effortless shift last season from the I-League into the ISL. This year they remained atop the table at the New Year break, and their captain says he sees the game itself differently now, with a broader spatial awareness added to his experienced playbook.

The goalscoring game-changer of JCT is now game-reader at BFC, except playing at a higher pace and added physicality from when he was younger. Chhetri chooses simile over metaphor: "Right now" he says, "I am like a potato." He's not talking about his shape - which compresses age, physiognomy and experience into the motion efficiency of a human bullet - but rather all- round utility.

The longest stint of Chhetri's 18-year career has been at Bengaluru FC. JSW

We are on the terrace of the BFC office, in the never-to-be-completed Bangalore Football Stadium. Chhetri is shouting out instructions to the BFC Under-18s taking a penalty in a Youth League match.

"Right side, right side," he yells. For whom? Penalty taker or the goalkeeper? The teenagers' knees could be shaking. Chhetri is grinning and offers no clues. He often says he had never imagined how far football would take him and that he targets are simple, day by day.

Fine, fine, but every high performing athlete owns a switched-on competitive mongrel and a burning kernel of ambition. Whatever his public persona, those gatekeepers of his destiny - competitiveness and ambition - is what drove a "fat little kid" (Renedy's words) from Delhi Cantt to, as coach Derrick Pereira describes it, "the outstanding player who is the face of the country's football."

Pereira says, "We are lucky to have Sunil in the national side. How Sachin Tendulkar inspired young cricketers 20 years ago and Kohli is doing now, Sunil Chhetri will inspire young footballers." Renedy slots him in amongst the great strikers of the last three decades with IM Vijayan, Bhutia and Jo-Paul Ancheri. Bhutia says Chhetri is "definitely one of the greatest Indian players to have played the game."

Former India coach Houghton remembers "a bright boy, with the ability to consume information and use it to benefit his game. He had that real ambition... a lot of players who were talented but didn't that have that ambition. Sunil definitely had it... He deserves his career, he has worked hard at it."

Steven Dias recalls being dragged out to gym after morning training, Chhetri's extra hours of individual practice and workouts in the room to build core strength, the solitary morning runs. "When he was picked for India, he was third or fourth striker. I saw him do what every player should have done. I used to respect him for it." Just turned 20, the two would chatter on in awe about sharing space with the legendary Bhutia, but Dias could see that Chhetri "always wanted to be the best, in his position, whichever club he played for, the best. Even the highest-paid at a club, even if it was one rupee more than the next guy.. not in a bad way" he laughs, "but just the best." Ahead of everyone. At the top. Which is where he now sits.

Chhetri is animated discussing the need for abundant playing numbers from a young age - be it baby leagues or under-10s onward. "When everything comes together, there is so much to choose from. There will be 30 Gurpreets every year, 30 Udantas every year." Then in mischevious rush, he adds, "Only-one-Sunil-Chhetri-by-the-way" and chuckles.

Tickets to the India vs Kenya match at the Intercontinental Cup in Mumbai last year were sold out after Chhetri's appeal to fans to support Indian football. AP Photo/Rafiq Maqbool

What do I answer people?

BFC under-18s, starlight in their eyes, are whispering and clustering at a respectable distance, sneaking remote selfies from around where Chhetri is chatting. Chhetri speaks like he plays, at speed, nimble, mind faster vocal chords. In a footballing environment of much smoke, mirrors and loud noises, it is a relief the captain of India owns proportion. Indian football is not fancy; it stands, he says, for labour and sweat. "We are a country who are not as skilful but are very hard-working. We are a footballing nation where the boys listen and are ready to put in the hard work." A rich skill bank belongs to deeper footballing cultures. "A Scottish batsman will never have the hand-eye coordination of a Sehwag because cricket is... here, everywhere from every age. A Brazilian player's touch will never come in a Bangladeshi player -- I'm not trying to demean anyone, it's just the way it is."

The current India national U-16 squad he points out is "miles better" than the u16s he played for. "I just hope the teams coming after them are better than this one -- that's how you improve." His dream for India's football is constant improvement but at a faster pace. "If you ask me to put a number, I want us to reach in the top 10 in Asia and stay there.... Then we rub shoulders with the best in Asia, top five or six. Then you know it's there. Right now, we can't even see, it's all foggy, blurry..."

For the there and the it, Chhetri's gesticulating towards a visible distance, trying to explain in real terms how far away India is from the goal that is the Grail. The real immovable goal, that is, rooted in ground reality. Not the one that is constantly shifted by the AIFF and its varied consultants every few years -- a shot at the World Cup. Mattering in Asia means fair assessment. "Once you can see us playing Australia, Japan, South Korea, they can see, 'Oh, they lost 2-0, 3-0, 2-1, whatever.' They know that's how far we are. Right now, what do I answer people?"

Answer the questions he gets asked a thousand times -- when is India going to play in the football World Cup? Chhetri said he was in tears when he saw the first match of the 2017 U-17 FIFA World Cup. It's his wish, "I hope I'm in the stands ... Before I die [I hope] I see my country playing World Cup. We all want that."

Due to his free-speaking persona, Chhetri has become a credible voice for Indian football. Amongst non-cricketer male athletes, Chhetri's Twitter following (1.53m) in India is third after boxer Vijender Singh (3.76m) and wrestler Yogeshwar Dutt (3.56m). His heartfelt June 2018 Twitter video asking fans to come to the watch the team play in the Intercontinental Cup in the 7,000-seater Mumbai Football Arena, not only filled the ground but also became India's most retweeted tweet (about 60,000 times) in 2018.

This is nothing but a small plea from me to you. Take out a little time and give me a listen. pic.twitter.com/fcOA3qPH8i - Sunil Chhetri (@chetrisunil11) 2 June 2018

Chhetri doesn't think about it any more. "I had no clue it was going to turn up the way it did. It wasn't any gimmick, there was no script. It was just me being sad before the next game... we had beaten Taipei and the lads, coming-up lads like Udanta [Singh] and [Anirudh] Thapa they did so well and there were only 2,000 people in the stadium."

But there is no moaning about Indian football's failings. "There is no resentment or regret. I never compare myself with Sardar Singh or Virat Kohli or Saina Nehwal or Sania Mirza or anyone. All our lives, our journeys, our difficulties, our rewards are different."

To go full-fledged

When Chhetri received his first salary as a 17-year-old Mohun Bagan prodigy, it was in a four-month advance of around Rs 60,000 a month, at a time his father KB Chhetri was earning Rs 22,000 from the army. Chhetri withdrew the entire cash from an ATM over three days, set the notes out on his bed and looked at them. "I thought MY GOD, I am the richest guy in the world." He threw the money into the air in a mini-shower, and then went to a mall and "bought anything and everything that I could...jeans, shoes, sunglasses. It was mad." Before Kharga Bahadur turned up and sternly informed his son that was "not the way to live". Today, Chhetri is the highest-paid Indian football player, retained by BFC at Rs1.5 crore a season at the 2017 ISL auction.

Even though he belonged to a family of two football internationals from Nepal (his mother Sushila and her twin sister) and a father who played while serving the army, in the Corps of Electronic and Mechanical Engineers, football was always meant be a tool of discipline and fitness, not a career option. The words of his Army Public School (Delhi Cantt) football coach, "a great man, Mr Ghale," never left Chhetri, "Work hard, kid because good things are going to happen to you." He says, "I could probably never see what he was seeing." When he heard Ghale say, "If you do well, you might play for Delhi," he did not think it possible, but never forgot the words.

His backstory is one of an obstinacy, to check if what his schoolteacher said could be made to happen. Chhetri switched to a footballing school Mamta Modern by himself to against his family's knowledge - angry father, distraught mother. Chhetri then moved out at 15 because he "wanted to go full-fledged" and lived in the hostel, full of footballing nuts from around the country. Cold war broke out when his father returned from a non-family posting and learnt of the move.

One day, KB came to watch his wilful son train from the stands and began to return frequently, ferrying "nuts and chawanprash [a health food]" to supplement hostel cooking. The ice thawed and the two spoke. "And I told him, 'I know I've hurt you, but this is something that I really want to do and I'll give my best.'"

Also read:

-Chhetri backs India's ability to frustrate Asian Cup opponents

-'From the last bench, I sit in the front now'

-Chhetri and Bhutia, first among equals

The bizarre career path appeared to be working. The next target was Delhi's prestigious St Stephen's College -- which required 70% marks and a place on the India junior team. He had topped his school in Class XI in the commerce stream and impressed at the Durand Cup, playing for City FC. But before college life took hold of Chhetri, Mohun Bagan turned up, contract and future in hand. Whatever Mr Ghale had seen, the oldest club in India was seeing, only in higher definition.

The game and competing with mind and body on high alert consumes him. He has never been red-carded, but knows his furies need to be channeled. "I want to be calm and composed," he says. "I like me when I am calm and composed. I don't like when I get angry -- because I'm so full of emotion that if I let it all out on being angry, then it all goes out."

BFC media manager Kunaal Majgaonkar has popped in and out of our conversation, the two men colleagues and buddies. Soon stories emerge from nearly five years ago over disputed games of carrom and Monopoly, originally begun to kill time. On both occasions (sum and substance), the game was suspended after Majgoankar said he was stepping away due to arguments over rules with Chhetri. Over the carrom, Chhetri smashes his fist on the board, fractures his hand ("What am I going to tell the coach? We fabricated a story that I fell in the bathroom."), hurls a coin which flies through the air and cracks a giant TV in the BFC game room. The melee over Monopoly at Calcutta airport led to collars being grabbed (Chhetri did the grabbing), with the other two Monopolists, open-mouthed, mystified. The seriousness of yesterday has turned into absurdity today and both men are laughing. (Oh, and he quickly bought a new TV to replace the screen shattered by a flying carrom coin).

On both occasions, Chhetri understood arguments over rules, it was the walk-away that had set him off. "Tell me how to fix the issue, but the game continues. Tell me how to fix the problem, but game khelo, na?"

Chhetri's numbers speak for themselves: 65 goals from 104 international appearances and 120 from 247 club appearances around the country. AP Photo/Rafiq Maqbool

Game khelo, na?

Houghton remembers conversations with the sparky, talkative forward he first met and says, "It's just a pity he couldn't get some period overseas where he played for some time and made himself into an international player really. His real ambition I'm sure was that he wanted to play in Europe. He really wanted to be one of the few Indians who could do good overseas. That was the one thing he impressed on me, that did I think he could play in Europe. I think he could have done, you know."

His odysseys overseas make for a gloomy recounting, but were treated like the launch pad that turned Chhetri into a titan for India. In 2009, a three-year offer from Queens Park Rangers couldn't go through because the British work permit for professional footballers mandates that their country must feature in the FIFA top 70. Ten months with the Kansas City Wizards / Sporting Kansas City (April 2010-Feb 2011) without game time because the coach invested in another player, had made him "negative" and had him return home. At Sporting Club de Portugal's B team (2012-13), he understood being told he wasn't ready for the first XI and sent to the reserves. There he trained alongside 19-year-olds who went far -- Joao Mario of Inter, 2016 European championships winner, Erik Dier of Tottehnam and Bruma of Leipzig being some of them. Chhetri returned home after nine months. "It wasn't that I was unhappy, that I wasn't getting chances. I was already 26-27 and couldn't not play. If I was 17 in Sporting, I would have stayed there. I had a four-year deal, I would have stayed. At 26-27 you need matches."

In sagely, measured tones, Houghton says, "You need a break, you need to go somewhere where the coach takes a liking to you and gives you a chance and gives you that confidence, and Sunil had that ability, just like Bhaichung did, to play abroad. But he didn't get those breaks." In February 2013, Chhetri was put on loan to Churchill from Sporting CP. In July, he signed with newly formed I-League club Bengaluru FC. When the career-defining break came, Sunil Chhetri made sure he caught it. Suddenly, the whole wall moved.

The first time I met Chhetri, a few days after his two goals at the Kanteerava in Bangalore, BFC becoming the first Indian club to enter the AFC Cup final, the cup final of continental clubs. The first goal had come off a set-piece header, the second was a thing of beauty. Given space on the left, Chhetri went around a defender and away from the goal. Three opponents in front of him, two behind them blocking the line, the keeper with his zone covered. From around 70ft away, Chhetri finds time and space to send up a right-footer. The ball rises well over the defending block, its curling dip evades the goalkeeper's outstretched arm near the left corner, and sinks emphatically into the back of the netting. AFC Cup final, here we come.

The goal plays itself out in my mind's eye and in front of me is the compact young man who scored it. "How cool are you?" I ask.

Suit sharp, disposition on high beam, Chhetri shakes hands and with modestly-controlled glee says, "Quite decent."