MADRID — Aryna Sabalenka finally lost a tennis match. Hailey Baptiste took it from her.

Sabalenka, the world No. 1, had won 15 consecutive matches across three tournaments and looked on her way to 16th until Baptiste, the quickly improving American with a smooth all-court game and a dangerous mix of power and spin, caught fire in the second set Tuesday night.

Baptiste barely missed long stretches, carried the momentum into the third set and outlasted Sabalenka down the stretch in a nail-biting sequence of games and then a tiebreak for a 2-6, 6-2, 7-6(6) win. Baptiste saved six match points, inflicting Sabalenka’s first defeat having held even one since the 2023 Madrid Open.

The American appeared to confuse Sabalenka with the combination of her slice backhand and whipping forehand. For a good while, Sabalenka spent as much time twisting her neck to watch balls whizz past her as she did setting up winners of her own.

Sabalenka has been mostly flawless this year. She was 26-1 coming into the match against Baptiste. Her lone blemish was a loss in the final of the Australian Open, where Elena Rybakina beat her 6-4, 4-6, 6-4.

Baptiste appeared to get the decisive break in the seventh game of the third set, unleashing a series of heavy, topspin forehands that darted into the clay just ahead of the baseline. They were the kind of balls that Sabalenka has tortured opponents with all season.

But Sabalenka broke right black, blasting a crosscourt backhand to even the score at 4-4. Sabalenka held serve and had four match points with Baptiste serving at 4-5. Baptiste smacked an ace to save the first one and cracked an inside-out forehand to save the second. Baptiste serve-and-volleyed on her second serve to save the third. Then she did it again on the fourth, inducing a wide backhand from Sabalenka. On the fifth, a drop shot and lob volley combination got Baptiste out of trouble.

Two points later, she zipped a backhand down the line to knot the set at 5-5 and put the pressure squarely onto the other side of the court. From there Baptiste played free once more. She attacked Sabalenka’s serve. She cracked a forehand winner down the line and got the break when Sabalenka sent a forehand several feet off the court.

Now she needed to close out the world No. 1. Sabalenka helped her by netting an easy chance at a backhand put-away. But then Sabalenka found the court on a couple of big returns and off they went to a tiebreak.

Advantage Sabalenka, the best tiebreak player in the sport. At 4-3, she hit a nifty drop volley from inches above the clay to move two points from the match. But Baptiste went on the attack and drew even at 5-5.

A forehand long gave Sabalenka a sixth match point, this one on her serve. She missed a backhand down the line by inches, then hit a forehand into the net to give Baptiste her first match point.

That was all she needed. A crosscourt forehand to the postage stamp finished it. She spread her arms, allowed a brief smile, the kind that had crossed her face when she was double-faulting and having to dig deep late in the third set, and made her way to the net for a handshake.