Roger Federer and Rafael Nadal will meet for the first time since 2017 in Indian Wells after the Spaniard defied more knee problems to defeat Karen Khachanov.
Nadal took a medical time-out after the third game of the second set to have tape applied under his right knee and looked in serious discomfort before battling to a 7-6(2) 7-6(2) victory, saving a set point to avoid being pushed to a decider.
Federer, who is looking to follow up his 100th title in Dubai last month, had a more comfortable outing in ending the run of young Pole Hubert Hurkacz 6-4 6-4.
With the last-four clash taking place on Saturday, there must be a question mark over whether Nadal will be fit enough even to start the match, and certainly whether he will be able to bring his best against Federer.
Assuming he does take to the court, Nadal will face his great rival for a 39th time, looking to improve his winning record to 24-15.
But recent history favours Federer, who has won all five of their matches since 2014, including in the fourth round here two years ago.
Their last meeting came in the final of the Shanghai Masters in October 2017, which Federer won 6-4 6-3.
Nadal told Amazon Prime: "I had some troubles with the knee. It was some tough moments but I was able to fight and finally find a way.
"Hopefully I will be ready (for the semi-finals), I'm going to try my best to recover and play one of these matches that I want to play."
