LOS ANGELES • An emotional Juan Martin del Potro could barely believe he had finally won a Masters 1000 series title at the 51st attempt at Indian Wells on Sunday but is determined to keep the trophies coming in his late career renaissance.

The 1.98m Argentinian with the big forehand endured years of injury-induced heartbreak but was at the top of his game in the Californian desert, beating world No. 1 Roger Federer 6-4, 6-7 (8-10), 7-6 (7-2) in an enthralling final.

"It's so big," the 2016 Olympic silver medallist said after his biggest individual triumph in nine years.

"I'm still shaking. I cannot believe I won this tournament, beating Roger in a great final and level of tennis.

"I'm number six in the world, I think? Which is so good to me. And I'm excited to keep working... I just want to keep winning titles like this if I can."

Del Potro was tipped as a future world No. 1 in 2009 after the then 20-year-old reached the Australian Open quarter-finals and the French Open semi-finals before capturing his maiden Grand Slam at Flushing Meadows.

He failed to break the dominance of Federer, Rafa Nadal, Novak Djokovic and Andy Murray, though, and a string of career-threatening wrist injuries almost forced him to give up on tennis.

"I was close to quitting tennis because I had three surgeries on my wrist and I couldn't fix the problem," he said.

"I got depressed at home for a long while, and I wasn't happy doing the effort to recover my wrist.

"That's what I was thinking about, quitting tennis. But thank God, I'm here and healthy, and I'm playing tennis again. I'm doing this because I love it."

He has regained form over the last two seasons but, although he entered the final on a 10-match winning streak after clinching victory in Acapulco for his 21st singles crown last month, he was still the underdog against Federer.

However, del Potro can now drive his backhand effectively with two hands again without having to rely on a one-handed slice.

He saved three match points and blew one of his own as he snapped Federer's 17-match streak this year.

"It was an unbelievable match. We played a great level of tennis. The people were excited on every point. Maybe I'm in better shape, because a few years ago, I never win a title like this," he added.

"I'm surprising myself. I don't like to compare this time with a few years ago, but I'm just enjoying what I have to do every day... I'm so happy for that.

"The first thing is try to be healthy during the whole year and play where I like to play.

"Now I have to do a smart schedule on clay to feel 100 per cent for the rest of the season."

Del Potro will compete in this week's Miami Open, where WTA Indian Wells champion Naomi Osaka will face former world No. 1 Serena Williams in the first round.

He was tight-lipped on his celebration plans. "I cannot tell you," he joked of his party agenda.

"It will be Miami, maybe tomorrow, but that's enough."

Federer, who will remain on top of the rankings no matter happens in Miami, was magnanimous in defeat and praised his opponent.

"Not much in between us, but you deserve it," the Swiss told del Potro at the trophy ceremony. "Well done. Enjoy the moment."

AGENCE FRANCE-PRESSE, NY TIMES, REUTERS