He speaks surprisingly softly for a man who stands 6ft 6in tall, but Juan Martin del Potro became one of the big noises in tennis with his victory over Roger Federer in the final of the US Open here on Monday night.
The new world No 5, who will celebrate his 21st birthday next week, has been threatening to make his major breakthrough ever since losing to Andy Murray in the quarter-finals here 12 months ago and claimed his first Grand Slam title by beating the best player in the history of the sport 3-6, 7-6, 4-6, 7-6, 6-2.
With a big game and a physique to match, the youngest player in the world's top 10 sees plenty of room for improvement. "I have many things to improve to be better," Del Potro said after his four-hour victory, which denied Federer a sixth successive US Open title.
"Of course I would like to be in the top four or top three, or even to be No 1 in the future, but I will have to play like today for many, many weeks in the year. If I carry on working and still go in the same way, maybe in the future I can do it."
The title capped a year of outstanding progress by Del Potro, who won his first tournament on the main tour only last summer. Before Wimbledon last year he was ranked No 62 in the world, but by the end of 2008 he had climbed into the top 10. His previous best Grand Slam performance had been at this summer's French Open, when he lost a five-set thriller to Federer in the semi-finals.
Unlike most of his fellow countrymen, Del Potro feels more at home on hard courts than on clay. This was the title on which he had set his sights. "It's difficult to explain this moment," he said after beating Federer for the first time in seven attempts. "Since I was young I've dreamed of winning this trophy."
Guillermo Vilas, the last Argentine to win here, 32 years ago, was in the crowd, though not in Del Potro's guest box, in which only three of the 15 seats were taken. Federer, in contrast, was supported by a large group of family and celebrity friends, including his parents, Gwen Stefani, Gavin Rossdale and Anna Wintour.
Del Potro is the latest tennis talent to emerge from Tandil, an Argentine mountain city about 150 miles from Buenos Aires. Remarkably, six tour players in recent times have come from Tandil, which has a population of about 100,000: Juan Monaco, Mariano Zabaleta, Maximo Gonzalez, Diego Junqueira, Guillermo Perez-Roldan and Del Potro. The common denominator is Marcelo Gomez, who has coached them all. Del Potro started working with him at the age of seven and says his secret is that he keeps things simple.
Much the same can be said of Del Potro's game. Although he has a good touch – he produced one of the shots of the tournament with an exquisite stop volley winner against Marin Cilic despite the fact his opponent was standing on the edge of the service box – his great strengths are his big serve and even bigger forehand. In the final he hit 37 forehand winners to Federer's 20, a remarkable statistic considering the Swiss is reckoned to have one of the best forehands in the history of the game. For the last 18 months Del Potro has been coached by Franco Davin, who helped Gaston Gaudio win the French Open five years ago.
A golf coach who worked with Angel Cabrera, a former US Masters champion, once said that Argentina's great success across a range of sports could be explained by "meat and potatoes". Tandil is especially famous for its beef and Del Potro, who is also a keen footballer, is built like a man who enjoys the local fare.
There is a growing trend for taller players to succeed in tennis, but, unlike some, Del Potro adds strength to his height, without losing athleticism. At the end of four hours against Federer he was still moving freely and with surprising grace.
The questions on Monday were not so much about his talent as his ability to handle the occasion. On the morning of the match he had been so nervous he could not even eat breakfast. Tense and edgy in the opening set, he lost the first three games.
Having dropped his serve in the first game of the second set, Del Potro looked likely to go the way of Novak Djokovic and Murray, who both lost to Federer in straight sets here in their first Grand Slam finals. But he quickly played his way into the set and was soon striking the ball with the power that had sent Rafael Nadal to his heaviest Grand Slam defeat in the semi-finals.
The Argentine also showed he has the mental strength to cope with the biggest moments, saving 17 of the 22 break points against him and winning both tie-breaks. Federer served poorly, hitting 11 double faults and only 13 aces, and allowed himself to be distracted by his recurring bugbear, the video replay system.As the match progressed the crowd warmed to the underdog, who high-fived spectators in the front row after one dramatic point. Federer was within two points of victory when Del Potro served at 4-5 in the fourth set, but two big serves and a crunching forehand kept him at bay. Del Potro quickly took control of the final set and kept up the pressure to the end, Federer saving two match points before putting a backhand long.
If it was a surprising end to Federer's Grand Slam year, his defeat should certainly be put into perspective. The world No 1 played in all four finals, winning two of them to complete his set of Grand Slam crowns and overtake Pete Sampras's record of 14 major titles. This was the first time he had lost a Grand Slam final to an opponent other than Nadal and ended his run of 40 consecutive victories at Flushing Meadows.
The decider bore similarities to the last set in the Australian Open final, which Nadal won by the same score as Federer's challenge faded quickly. "I almost don't remember the match in Australia," Federer said. "I felt like today I was much more in control. I had many more chances. It's one of those finals that I may look back on and have some regrets about. In the end, he was just too tough."
He added: "I'm playing great tennis right now. This doesn't take away anything from how much I've achieved this year. I've had a wonderful season in terms of Grand Slams."
Rising power: Del Potro's 2009
Career prize money: £4.4m
Prize money in 2009: £3.1m
US Open prize money: £1m
Grand Slam record 2009: Australian Open: QF; French Open: SF; Wimbledon R; US Open: Champion