Daria Kasatkina has upset Venus Williams 4-6 6-4 7-5 in a nearly three-hour baseline struggle to reach the final of the Indian Wells Masters.

Kasatkina was two points from defeat, trailing 4-5 and 0-30 in the third set when Williams committed four straight errors.

Williams won just two more points as Kasatkina took the last two games to close out the match in 2 hours, 48 minutes.

After shaking hands, Kasatkina pumped her fists and shook her head slightly as if in disbelief at beating the 37-year-old American and advancing to the biggest final of her young career.

When she wasn’t trading shots from the baseline, a nervy Kasatkina fooled Williams with drop shots, including two that landed just over the net near the sideline.

The Russian tossed up lobs over the 6-foot-1 American – some worked, some didn’t, but she was undeterred.

There were 14 service breaks in the match.

Williams rallied from 3-1 down to win the first set. She trailed 3-1 again in the second and tied it 3-all when Kasatkina was broken on a double fault.

Kasatkina won the last four games in a row to take the second set. The players duelled through eight deuces in an epic eighth game, with the Russian turning back six break points against her. Williams pulled a forehand wide to lose the game.

Williams next served a love game to go up 5-4 but then double-faulted twice in a row to drop serve and trail 6-5.

Kasatkina won on her second match point when Williams netted a backhand.

Top-ranked Simona Halep will take on Naomi Osaka, a 20-year-old from Japan, in the other semi-final.