Yet the tall, gentle Argentine with the crushing forehand was the original “Next Gen” player when he did the unthinkable and beat Roger Federer to win the 2009 US Open title.
The mighty Federer was homing in on his sixth consecutive New York title, he had won Wimbledon and the French Open that year and so beaten Pete Sampras’ then record of 14 career grand slam titles. He was also two sets to one up in the final. And then Del Potro relaxed, played as he knew he could and won his first – and (to date) only – major title.
Today the pair meet again in the quarter-finals. Federer leads their rivalry with 16 wins to five losses but that does not seem to matter when Del Potro, the world No 28, scents history.
On Monday night, the Argentine was on the verge of pulling out of his match with Dominic Thiem, the world No 8 and one of the ATP’s much vaunted new talents. Struggling with a virus, Del Potro was a set and 4-1 down and he felt lousy. But then, as the crowd cheered for more, he pushed himself on and somehow – not even he is quite sure how – managed to win 1-6, 2-6, 6-1, 7-6, 6-4.
“I was trying to retire the match in the second set,” Del Potro said. “Then I saw the crowd waiting for more tennis, waiting for my good forehands, good serves. I took all that energy to change in a good way and think about fight and not retire.
“I did well, and I start to enjoy little bit more about the fans. I think I did everything well after the third set.”
Del Potro, though, is good at comebacks. Since he won the title eight years ago, his career has been blighted by a series of wrist injuries, all of them potentially career-ending.
Yet he has fought his way through them and now he has the chance to relive the greatest moment of his professional life and put himself one step closer to another major title.
“Is going to be interesting match for play,” said Del Potro. “It will be after eight years again in the central court of this tournament. I know how to play if I want to win.
“I think the people love my effort to come back and play tennis. They know what have been through with all my wrist problems. They like one guy who never gives up, and he’s trying to play tennis.”
Federer, pictured right, who breezed past Philipp Kohlschreiber 6-4, 6-2, 7-5 on Monday has played better in the last couple of rounds but he knows Del Potro is a serious threat.
That loss in the final all those years ago still stings and he knows that the Argentine could do for him again if he is not careful.
“I felt like that I left that match with a lot of regrets,” Federer said.
“It probably feels like one of those matches I would like to play over again. It ended my five-year reign here in New York.”
Federer, so used to being loved by every crowd in every stadium around the world, knows that the New Yorkers love an underdog and that, when Del Potro has the crowd behind him, as he did on Monday night, anything is possible.
“I know the people like when I hit hard with my forehands,” Del Potro said. “The people stand up from the chairs when I hit good winners. I like to do that. When I feel that confidence to do my best shots, I know I can be dangerous for all the guys.”