"It's unreal", said Thiem. He twice called for a trainer, who applied tape just below Nadal's knee.
"My goal is to play on all the surfaces", he said.
But baseline specialist Thiem kept his composure and levelled the match in the second, gaining traction by extending rallies and unleashing a torrent of high-kicking serves to keep Federer off balance.
Andreescu had break points against her in each of her last three service games.
The 18-year-old Canadian's run is reminiscent of Naomi Osaka's path to last year's title.
Andreescu became the first wild-card to reach the Indian Wells final.
A smiling Andreescu was quick to correct a reporter.
"When she had the chances, she just go for it", Kerber said. "It was a insane match". The Ukrainian also was bothered by her inflamed right knee. "I feel fortunate for all the things I've done in my life and the world of tennis".
"You feel like every shot in Dominic's game has got some punch behind it", Federer said during his post-match press conference.
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"He's unbelievable in defense", Khachanov said.
Dominic knew he had to be aggressive to stand a chance against the opponent who likes to control the pace and he did that, hitting 24 winners and 25 unforced errors while Federer counted to 23 winners and 32 mistakes, spraying the most of those from his backhand wing. "He steps in and then he starts moving you, and then you are again in trouble".
It came in the very next game when Federer netted an easy forehand, blasting four winners on serve to gain a 4-1 lead and clinching the set in a mighty impressive way after landing four more direct points in game nine for a 6-3.
'It feels not real at all, ' added Thiem, the first Austrian to win a masters 1000 title since Thomas Muster at Miami in 1997.
Federer believes Nadal is playing better than he did in losing the Australian Open final to Novak Djokovic, who was upset earlier in the week.
"It is such a pleasure to compete with you, to learn so much from you, and to play with one of the biggest legends of all time", he told the 20-times Grand Slam champion during the trophy presentation ceremony.
Following the defeat, Federer said that though he is frustrated and disappointed to some extent, he admitted that Thiem was better than him when it really mattered.