INDIAN WELLS: Top-seeded Carlos Alcaraz beat Felix Auger-Aliassime for the first time in his career to book a semifinal clash with Jannik Sinner at Indian Wells.

Women’s top seed Iga Swiatek lined up a last-four grudge match against Elena Rybakina, who stunned the Polish world No. 1 in the quarterfinals at the Australian Open in January.

Alcaraz posted his first victory over Auger-Aliassime in four meetings with a 6-4, 6-4 win to keep his bid to regain the world No. 1 ranking on track.

“It’s wonderful to beat Felix finally, and the way I did it, playing at a great level,” said Spain’s Alcaraz, 19, who called it perhaps his best match of the season.

Italy’s Sinner reached the final four with a 6-4, 4-6, 6-4 victory over defending champion Taylor Fritz and now has a chance to avenge his loss to Alcaraz in an electrifying quarterfinal at the US Open last year.

That five-set battle lasted five hours and 15 minutes, its 2:50am finish the latest in US Open history. Alcaraz would go on to lift the trophy and become the youngest world No. 1 in the history of the ATP rankings.

“We’ve played several times and all the matches have been very tough,” Alcaraz said. “I like this kind of challenge, I’m going to enjoy it.”

Alcaraz hadn’t dropped a set in reaching the quarters, but Auger-Aliassime was the first top-10 player he has faced this year.

This time, Alcaraz was ready for him, saying his prior defeats to the Canadian had taught him to “stay there.”

The two-hour clash was a thrilling display of athleticism and shot making from both players.

Alcaraz saved the first break point he faced as he served out the first set, but after he broke to open the second Auger-Aliassime — who saved six match points in a fourth-round win over Tommy Paul — promptly broke back to set the tone for a tense back and forth battle.

Auger-Aliassime had already saved two break points in the 10th game when Alcaraz gave himself another with a backhand volley winner, and with a break in hand he confidently served it out.

Sinner defied difficult, windy conditions to out-gun Fritz, gaining the decisive break in the ninth game of the third set when his pounding forehand to the corner forced the miss from the American.

Sinner polished it off with a hold at love after two hours and 17 minutes.

“I knew the last games would be tough to close it out,” Sinner said. “I just tried to play quite aggressively, which I’ve done.”

Swiatek, the defending Indian Wells champion and winner of the French and US Opens last year, swept past 83rd-ranked Romanian Sorana Cirstea 6-2, 6-3.

Wimbledon champion Rybakina, who fell to Aryna Sabalenka in the Australian Open final, outlasted 76th-ranked Czech Karolina Muchova 7-6 (7/4), 2-6, 6-4.

“She’s playing really well and in semifinals you always are going to play against the top players, so I’ll be ready,” Swiatek said of taking on Rybakina.

Swiatek, in her 50th week at No. 1, is vying to become just the second woman after Martina Navratilova in 1990-91 to win back-to-back titles at Indian Wells.

Cirstea did all she could to stick with Swiatek, recovering an early break and fending off a break point to level the first set at 2-2.

But Swiatek, adjusting to the warm daytime conditions after two straight night matches, won the next eight games to take a stranglehold on the contest.

Down 4-0 in the second, Cirstea clawed one back and held serve for 4-2 in a spirited display before Swiatek closed it out.

“The most important thing for me is that I came back in the second set to finish it properly,” Swiatek said.

Rybakina had all she could handle from the oft-injured Muchova. She needed three match points, wasting two with a pair of backhand errors before sealing it with her sixth ace of the day.

The other semifinal berths were decided on Wednesday, when Daniil Medvedev — chasing a fourth straight ATP title after victories at Rotterdam, Doha and Dubai — beat Alejandro Davidovich Fokina of Spain to set up a clash with American Frances Tiafoe.

Sabalenka also advanced, blowing away American Coco Gauff to book a meeting with 2022 finalist Maria Sakkari.