Sixth-seeded Czech Tomas Berdych became the first player to reach the men's semi-finals at the Indian Wells Masters on Thursday, beating Kevin Anderson 6-4, 6-4.
Berdych will play the winner of the night's blockbuster quarter-final between defending champion Roger Federer and Rafael Nadal. (Update: Nadal wins)
Nadal, the 11-time Grand Slam champion and former world No. 1 who is playing his fourth tournament since a seven-month injury absence, leads their career head-to-head 18-10.
Many of those duels have come on the game's biggest stages, and the most recent was Federer's semi-final victory over Nadal in the semi-finals here last year.
"We are both a bit suspect going into our match, so it's an interesting match-up," said Federer, who has yet to win a title this year and has been getting treatment for a sore back.
"It's not like a first round, but it still is early in the tournament. In the past this match used to be a final, now it's a quarter-final, so obviously it's a bit of bad luck of the draw for both of us."
Should Federer prevail, he'll get a chance to avenge a semi-final loss to Berdych in Dubai last month.
The Czech saved three match points en route to that victory, which denied Federer a title repeat.
No such heroics have been necessary here, as he has now reached the final four without dropping a set.
"It feels great," the 27-year-old said. "It's the first Masters of the year, it's very important for me for the confidence."
Anderson, who had surgery to remove bone chips from his right elbow in January, was the only unseeded player to reach the quarter-finals, with seven of the top eight making it through.
Berdych broke the big-serving South African in the final game of each set to secure the victory in 90 minutes, making it to the final four in the California desert for the first time.
He'll be gunning for his third final of the year, after runner-up finishes in Marseille and Dubai.