Though he seems young, the Argentine is already almost 30-years-old.
The Argentine stunned a raucous Indian Wells crowd that had been loudly backing Federer to continue his winning streak and secure the biggest win in the nine years since his US Open title triumph with a 6-4, 6-7 (8), 7-6 (2) victory.
The 36-year-old already has this year's Australian open title neatly tucked under his belt and it looked like he was marching towards yet another trophy at the Masters 1000 tournament at Indian Wells this past weekend.
"I was close to quitting tennis because I had three surgeries on my wrist and I couldn't fix the problem".
The 29-year-old from Argentina handed Federer his first match defeat of 2018 and extended his own win streak to 11 matches, including a title run earlier this month at Acapulco.
After Del Potro took the first set, Federer recovered to win the second set, while Del Potro narrowly edged the final set after wasting two a match point.
Federer managed to win the second set but lost the third, meaning he surrendered his Indian Wells crown to Del Potro.
"It was disappointing", Federer said.
"But the first thing is try to be healthy during the whole year and play where I like to play". And I'm excited to keep working. The Argentine cashed in with a well-placed forehand in the corner to tie the set, 5-all. He needed two hours, 42 minutes and saved three match points to beat the World No. 1 in a tiebreak.
His celebrations, however, were short lived.
"It was worth everything I've been through to experience this moment", del Potro said. "The people were excited on every single point", Del Potro said.
Del Potro has persevered and conquered most of his doubts, but on Sunday, with Federer back across the net in the final of the BNP Paribas Open, del Potro had to be patient again.
All it lacked was a suspenseful third-set tiebreaker, but Federer's serve unexpectedly deserted him. I was still thinking about my forehand miss and my forehand error, mistake in the match point.
Osaka captured the title on her first match point by blasting a backhand into the open side of the court.
Federer is the defending champion there, too.
"I can not believe this moment". "Because you're always going to go through ups and downs in your career, or as a person for that matter". And for now, the sun is certainly shining on him. "Serving 40-15, any game I probably win - I don't know what the stat is - 90-something percent".
"If you put in a lot of hard work you can play well", said Osaka, who was playing in only her second final after being the runner-up in Tokyo in 2016.
"The question is how long?"
Juan Martin del Potro suffered serious wrist injuries through his career. It's a tough one. Which is so good to me.