Top seed Carlos Alcaraz downed Felix Auger-Aliassime 6-4 6-4 on Thursday to book an Indian Wells semi-final place against Jannik Sinner after the Italian knocked out defending champion Taylor Fritz 6-4 4-6 6-4.
US Open champion Alcaraz got off to a flying start, forcing the Canadian to save four break points before landing an inch-perfect forehand winner to break for a 3-2 lead in the opening set.
Auger-Aliassime grew into the match in the second set as the pair traded early breaks but Alcaraz was able to ramp up the pressure and take a 5-4 lead following an errant backhand from his opponent.
The 19-year-old Spaniard served out the set to secure a first win over Auger-Aliassime and make the semi-finals of the tournament for a second straight year.
"My goal today was to stay in it, and I played probably one of my best matches this season, so I'm really happy," Alcaraz said.
"He has a great first serve, and this is the first time I broke his serve, so I'm happy with that. I'm looking forward to playing Sinner again, we've had some great battles."
Sinner, 21, was sharp from the outset in his match against American Fritz, riding an early service break and fending off a break point to take the first set behind his solid baseline game.
Fourth seed Fritz responded in the second, breaking Sinner on set point with a backhand winner that brought the crowd to their feet.
An exchange of breaks kicked off the third and Fritz smacked a forehand winner for a 4-3 lead but 11th seed Sinner took control from there.
He leveled at 4-4 with an athletic overhead, broke for a 5-4 advantage and blasted a serve Fritz could not handle on match point, the American's backhanded return sailing long to end the engrossing contest in the Southern California desert.
Meanwhile, World number one Iga Swiatek continued her pursuit of back-to-back Indian Wells titles as she cruised past Romania's Sorana Cirstea in straight sets to reach the semi-finals.
The 21-year-old beat Cirstea, ranked 83 in the world, 6-2 6-3.
The defending champion won eight consecutive games en route to a comprehensive victory in California.
Winner of the French and US Opens last year, Swiatek will face Wimbledon champion Elena Rybakina on Friday.