Rafael Nadal withdrew from the Indian Wells tournament on Saturday with a knee injury, shortly before his eagerly-awaited semi-final clash with great rival Roger Federer.
It would have been the 39th meeting between the pair and the first since 2017.
"I warmed up today and I felt that my knee was not good to compete at the level I needed to compete in semi-final," Spain's Nadal said in a statement. "It's tough for me to accept all these things that I'm going through in my career."
The knee had begun to bother him in the second set of his 7-6(2) 7-6(2) victory over Karen Khachanov in the quarter-finals on Friday.
Nadal had enjoyed a dominant week at Indian Wells, reaching the semi-finals without dropping a set.
"For me it is not about today only," the world number two said.
"It's about what it means for me to have to pull out in a tournament that I love so much like this one, and in the semi-finals after playing well during the whole tournament. You can imagine that I can't be happy."
Nadal, who has struggled with knee injuries throughout his stellar career, was the second high-profile player to withdraw from the tournament.
Last Sunday, Serena Williams retired from her match against Garbine Muguruza with what was described as a viral illness.
Federer, 37, will play either Milos Raonic or Dominic Thiem in the final, bidding for his 101st career title.
