INDIAN WELLS, Calif. -- Rafael Nadal withdrew from the BNP Paribas Open on Saturday, done in once again by a knee injury.
He had been set to play longtime rival Roger Federer in the semifinals.
A somber Nadal announced his withdrawal a couple of hours before he was scheduled to take the court at Indian Wells Tennis Garden.
"I warmed up today in the morning, and I felt that my knee was not good enough to compete at the level that I needed to compete," he said.
Federer was warming up on another court at the same time as Nadal and figured the match was on. However, Nadal soon texted him it wasn't going to happen.
"It's a big letdown," said Federer, who came on court in khaki shorts and a gray cardigan to address fans. "I know the anticipation is there from the crowd and also us players. I'm excited to be in the finals but not this way."
Federer will face Dominic Thiem, who defeated Milos Raonic 7-6 (3), 6-7 (3), 6-4, in the final.
Against Raonic, Thiem earned the only break of the third set in the fifth game. He led 5-3 and served it out, winning on his second match point with a backhand volley.
Thiem and Federer have split their four previous meetings, with only one going three sets. Federer won the last time they played at the ATP Finals in London in November.
Nadal's right knee flared up in the second set of his 7-6 (2), 7-6 (2) victory over Karen Khachanov in Friday's quarterfinals. He twice called for a trainer, who applied tape just below Nadal's knee. It was obvious that Nadal's movement was hampered.
Nadal said he won't play again until the Monte Carlo Masters on clay in mid-April.
"I don't have doubts today that I will be ready for Monte Carlo," he said.
Knee problems have dogged the 32-year-old for years, and they cut short his 2018 season after the US Open in September, when he was forced to quit two sets into his semifinal against Juan Martin del Potro.
Nadal choked up discussing his withdrawal last fall, and he appeared near tears Saturday.
He admitted that he sometimes is sad because he feels at a disadvantage against his opponents due to his continued knee issues that force him to limit his practice and playing time.
Then he gathered himself, saying, "It's not the moment to complain much. With all this stuff, I still where I am today."
The year began promisingly enough. Nadal didn't drop a set in reaching his fifth Australian Open final, where he lost to Novak Djokovic. He is ranked No. 2 in the world and has a match record of 11-2.
"Still tough because I felt more or less OK during this beginning of the season in terms of my knee," Nadal said. "Now it starts the process that I have to decide what direction we have to take to recover well and to recover as soon as possible."
Even with all his injuries, Nadal indicated he has no intention of giving up playing on hard courts, the surface for two of the four Grand Slam events.
"My goal is to play on all the surfaces," he said.
It would have been the 39th career meeting between Nadal and Federer, who advances to Sunday's final in pursuit of a record sixth title at Indian Wells and the 101st in his career.
"I know every one we have now could be our last," Federer said. "It's a special rivalry, maybe the most special with Rafa and Novak."
With time to fill before the women's and men's doubles finals, Djokovic and Pete Sampras teamed for a one-set doubles match against John McEnroe and tournament director Tommy Haas. Comedian Jon Lovitz served as chair umpire.