Alexander Zverev's quest to win just his second title since 2024 ended abruptly as he was dumped out of the Mexican Open by Miomir Kecmanovic.

World number four Zverev was the top seed in Acapulco, but Kecmanovic pulled off an upset to reach the quarters.

Kecmanovic clinched a 6-3 6-7 (3-7) 7-6 (7-4) victory, marking the first top-five win of his career.

"It feels amazing, especially because it's been a rough couple of years," said world number 84 Kecmanovic.

"So I'm happy that some things are going my way finally.

"I guess I was more aggressive when it mattered. I served a lot better than my usual standards, so I'm happy that things went well today.

"Obviously, he's the big favourite, so I didn't have any pressure there, but you still have to play well when it matters, close out the match and thankfully it went my way."

Upset in Acapulco @MioKecmanovic takes out the No. 1 seed, Zverev, to reach the @AbiertoTelcel quarter-finals. #AMT2026 pic.twitter.com/XxrXPo0lzZ

— ATP Tour (@atptour) February 26, 2026

Gael Monfils also lost, going down 6-3 6-3 to Valentin Vacherot.

Data Debrief: Zverev falls flat

A win would have made Zverev the player with the outright most victories at the Mexican Open since the event switched to hard courts in 2014, overtaking Rafael Nadal.

Instead, the German will have to wait at least another year to achieve the feat, while Kecmanovic celebrated ending a run of 11 straight defeats against players ranked in the top five.