The semi-finals of the WTA’s Indian Wells Masters have both ended in massive upsets, with Venus Williams and World No.1 Simona Halep both bundled out by much lower-ranked opponents.

Daria Kasatkina beat Williams 4-6 6-4 7-5 in a nearly three-hour baseline struggle, while Naomi Osaka made much quicker work of Halep, routing her 6-3 6-0 in 64 minutes to set up a final between the two 20-year-olds.

In the first match, Russia’s Kasatkina was two points from defeat, trailing 4-5 and 0-30 in the third set when Williams committed four straight errors and then dropped the last two games to close out the match in 2 hours, 48 minutes.

“If I don’t win, I’m not happy,” Williams said. “You don’t get used to losses, ever. Anyone who gets used to losses should give up on life.”

Williams breathed heavily during changeovers and was the last to leave her chair, while Kasatkina got up just as the umpire called time and jogged to the baseline.

Asked if she was tired, Williams said, “She just played better at the end. It was really pretty much that simple.”

After losing the first set, Kasatkina was visited by her coach on court. Philippe Dehaes told her, “She’s 37, you’re 20. Make her work a lot.”

Meanwhile, Osaka put away Halep on her third match point when the Romanian netted a backhand.

Ranked 44th, Japan’s Osaka opened the tournament by beating Maria Sharapova in the first round.

She beat No. 31 Agnieszka Radwanska and No. 5 Karolina Pliskova on her way to the final, dropping just one set in six matches.