The 24-year-old held off five match points as Sabalenka served for the deciding set and one more in the tie break before converting her 2-6 6-2 7-6 (6) victory in two hours and 30 minutes.
After the match, Baptiste harked back to a previous encounter with Sabalenka at the Miami Open in March and what she learnt from that experience to explain how she was victorious in Spain.
“I played her a few weeks ago and it was kind of a close match,” the world No. 32 said. “I just got broken once in each set.
“So I had a better idea of how to play her, and how I should play, adjustments I needed to make. So I think I just went in trying to play my game, still doing the same things that I’ve been doing, but I had a few adjustments I needed to make from the last time we played.”
She added: “The plan comes to my head when I get to the line. That’s what my brain was telling me to do … And it worked. It doesn’t always, but in that moment it did.
“It was an uncomfortable situation for her, me serving and volleying, hitting a drop shot in one of the match points. It’s not the easiest position to put her in, which is the plan.”
The pair split the opening sets and momentum swung back and forth in the decider with Sabalenka breaking first to take a 2-0 lead and then Baptiste breaking back to lead 4-3.
But Sabalenka once again broke the American to go ahead 5-4 and served for the set with five match points.
Baptiste, however, pulled out a wide array of winners to stave off elimination and keep herself in the game, drawing level at 5-5.
Baptiste had the chance to serve for the set but Sabalenka showed why she’s the dominant force of women’s tennis at the moment, breaking back and forcing a tie break.
Sabalenka had her sixth match point in the tie break but Baptiste once again held her opponent off, won the next three points and converted her only match point to seal the upset win.
The result snaps Sabalenka’s 15-match winning run and also makes Baptiste the first player to beat the four-time Grand Slam winner from match points down since Iga Swiatek in the 2024 Madrid Open final.
Baptiste also became the lowest-ranked player to earn a comeback win on clay against a world No. 1 in the past 40 years.
Afterwards, Sabalenka bemoaned her own mistakes and praised Baptiste’s courage as a reason for the result.
“I feel like in Miami I didn’t give her many opportunities,” Sabalenka said in her post-match press conference. “She couldn’t break my serve.
“Here, the first game, second set, I just double-faulted twice out of nowhere. It felt like that gave her belief. After that, she just started playing more aggressively. She was playing brave tennis. What can I say? Well done.”
Baptiste, who is into the Madrid Open semi-finals for the first time in her career, will face Mirra Andreeva.
Andreeva beat Baptiste at last year’s Wimbledon and she is out for payback this time round.
“Somebody else that I played before and lost to,” Baptiste said. “A little bit of a revenge tour, I guess. I’m looking to go out there and play my game again and get another win.”