"I'm still shaking", Del Potro said. I have everything what I want, and I want to keep improving my game to see what can I do. "I mean, we played a great level of tennis". I had very bad moments a few years ago and I don't want to think about that anymore.
The draw has put the world number one in the opposite half to the two heavyweight opponents.
They were on serve in the third until Federer broke for a 5-4 lead with a backhand winner off del Potro's serve.
Federer's attention will need to switch quickly to the next event on the tour, the Miami Open, which begins on Wednesday.
He is back in the top ten rankings this season for the first time since 2014.
"Roger and I were nervous during the whole match, and we felt that on court". "It's disappointing, but I thought it was a good match". But then during the [Rio] Olympics, after the [Novak] Djokovic match, my tennis life changed again. I can't believe I'm here and winning a Masters 1000, beating Roger.
Yes, del Potro is still lovable.
According to the tournament's official website, Federer said that he "has to get over" the loss.
"I have been content for a long, long time on the Tour".
Del Potro arrived in the Californian desert on the back of a title win in Acapulco but had far from a smooth ride against an agitated Federer, who simply would not give up on his quest for a sixth Indian Wells title. "And then be ready for Miami".
Federer had three match points while serving in the third set but he squandered them and played a poor tie-breaker to end up conceding the match to del Potro, who won his maiden ATP 1000 tournament Sunday.
"I'm not sure why the final record [with del Potro] is the way it is", Federer said. "It will be Miami, but that's enough".
"I let an opportunity like this go by". Yeah, Juan Martin was a bit better at the end. Overall he holds a commanding 18-7 lead but in finals, it's a different story, including the 2009 US Open which Del Potro won 3-6, 7-6 (7/5), 4-6, 7-6 (7/4), 6-2.
It had no effect on the outcome of the match.
Del Potro was competing in his first Indian Wells final since 2013, when he lost to Spaniard Rafael Nadal.