Korda notched his first victory over a world number one, sending Alcaraz to his second straight early exit in Miami, where Alcaraz lifted the trophy in 2022 but lost his second-round opener to 55th-ranked Belgian David Goffin last year.

It looked like Korda had missed his chance when he served for the match at 5-4 in the second set and was broken at love.

Alcaraz won the next two games to force a third set. The Spaniard stepped up his intensity, but Korda didn't buckle and it was Korda who seized a break for 4-3 in the third when Alcaraz sailed a forehand wide.

He held his next service game with confidence, slamming down an overhead winner on game point and after Alcaraz held serve to force Korda to serve for the match again, the American made no mistake, sealing victory on his second match point as Alcaraz sent a service return long.

"It feels great," said Korda, who has been ranked as high as 15th in the world but has endured two seasons disrupted by injury.

"I took the scenic route, that's for sure -- a little more stress than I would want but happy with how I played, happy with how I stayed with it.

"He's unbelievable in every aspect of his game, movement, volleys, forehand, backhand, there's nothing he can't do," Korda said of Alcaraz, who won the Australian Open in January to become the youngest man to complete the career Grand Slam.

The 22-year-old Spaniard had followed that up with a title in Doha and had pushed his unbeaten 2026 record to 16-0 before falling in the semi-finals at Indian Wells this month.

Korda will face either Spanish qualifier Martin Landaluce or 14th-seeded Karen Khachanov for a place in the quarter-finals.