Rafael Nadal saw off Karen Khachanov after Roger Federer had beaten Hubert Hurkacz in his quarter-final to confirm a meeting between the famous pair.
Nadal struggled through injury during the win, but he is yet to comment further on the pain, giving fans hope that the match will go ahead this evening.
Federer and Nadal have met a total of 38 times since they made their professional debuts in 1998 and 2001 respectively.
The first two meetings between the pair came at the Miami Open, with Nadal winning in 2004 and Federer winning in 2005.
Prior to Saturday’s match they have competed 38 times – and the younger man has the upper-hand in terms of previous results.
Nadal has won 23 of 38 meetings – Federer winning the other 15.
The surface has played a key role in the outcome of the results – and the outdoor hard court surface could make the difference in California.
The competition is almost even on a grass or hard surface, with Federer winning 13 of the 23 meetings.
However, Nadal leads the way on outdoor hard courts with eight wins to six over his Swiss counterpart.
In their overall careers, Federer has 100 titles to Nadal’s 80, but the younger man has a better win ratio.
Federer has won 1192 matches and lost 261 in ranked competition – a ratio of 82.04 per cent.
Nadal won 929 and lost 191 matches, giving him a ratio of 82.95 per cent.
Despite having the worse record overall, Federer has made a significant comeback in recent years, winning the last five games between the two.
Former British ladies No 1 Sam Smith gave her opinion of Nadal’s injury on Amazon Prime’s tournament coverage.
She said: “I think with Rafa, you know when he’s happy, when he’s confident. You know when he’s down, like he was a few years ago with his game.
“I think where he’s gutted actually, he knows he’s got to play Roger and he knows he’s never going to be 100 per-cent fit. No way. It’s going to be almost impossible.”