Roger Federer and Rafael Nadal will meet for the first time since 2017 in the Indian Wells semi-finals after winning their respective quarter-finals on Friday.
The fourth Swiss seed Federer, 37, has overtaken the Polish Hubert Hurkacz 6-4 6-4.
The second Spanish seed Nadal, 32, requested treatment on his right knee during a tough 7-6 (7-2) 7-6 (7-2) victory against Russian Karen Khachanov.
Nadal said that "we hope" will be ready for Saturday's semi-final.
"I will do my best to recover – these are the games I want to play," said the 17-time Grand Slam champion.
"Playing against my biggest rival in the later stages of our career and continuing to compete against each other is great."
The two greats played last in the Shanghai Masters final in October 2017, when Federer won in direct sets.
The 20-time Grand Slam champion has won each of the last five games, but Nadal leads 23-15 in their head-to-head record.
"I don't think those games are so important, actually," said Federer, who has yet to leave a set in this year's tournament.
"It's been a long time, unfortunately maybe because of the rivalry, for us or for me, it's always better to keep playing against him.
"Fans are perhaps more excited about us than they are because I always have to concentrate on my game.
"But it brings more and more energy into the stadium and for both."
& # 39; I was going through a difficult period & # 39;
Federer is chasing the sixth Indian Wells title – he is tied to Novak Djokovic five – while Nadal is looking for the fourth.
The other semifinal in California sees the seventh Austrian seed Dominic Thiem face the thirteenth Canadian seed Milos Raonic.
World number four Federer broke Hurkacz, 22, in the fifth game of the game, before doing it again in the third game of the second set and saving both break points on his service to win in 13 minutes.
Nadal had a much more difficult draw against the twelfth seed Khachanov, needing a medical suspension after the third game of the second set in which tape was applied under the right knee.
The number two in the world looked at him uncomfortably but saved a set point to avoid being led to a decider before impressing again in the tie breaker to secure victory in two hours and 16 minutes.
"I was going through a difficult time against a very, very difficult opponent," said Nadal.
"I managed to come back and have chances, but he served a lot, then I had problems with my knee, but I was able to fight and find a way."
BBC Tennis correspondent Russell Fuller at Indian Wells
A physio who runs in the field to apply straps to Nadal's right knee is all too familiar, but it remains a very sorry show.
Nadal showed before he could absorb the pain in the short term, and this was the first time he felt uncomfortable for fifteen days.
The same knee also needed treatment against Khachanov in the third round of the US Open last year. But Nadal was able to win that grueling game and then another two rounds, including a nearly five-hour victory over Dominic Thiem in the quarter-finals.
However, he had to retire in the semifinals – to close a year of immense frustration in which he was able to complete just one tournament on a hard court.
Nadal's participation in the Miami Masters next week must now be in doubt, but we only hope his knee can at least see him over the weekend.