Holger Rune of Denmark returns the ball during his first-round match against Alexander Zverev of Germany at the Tennis ATP tournament in Munich, Germany, April 27, 2022. (MATTHIAS SCHRADER / AP)

MUNICH - Danish teenager Holger Rune sealed the biggest win of his career at the Munich Open on Wednesday, outclassing top seed Alexander Zverev 6-3 6-2 for a spot in the quarter-finals of the ATP 250 claycourt tournament.

Rune broke world No 3 Zverev four times in a flawless performance for his first win over a player in the ATP top-10, ending the streak of the German who reached the quarter-finals in his previous five appearances

The 18-year-old Rune broke world No 3 Zverev four times in a flawless performance for his first win over a player in the ATP top-10, ending the streak of the German who reached the quarter-finals in his previous five appearances.

"It was a difficult match from the beginning," world No 70 Rune said following his victory over 2017 and 2018 champion Zverev at the Iphitos Tennis Club.

"He's in the top three in the world and has been playing some unbelievable tennis, especially in the past year winning so many big titles.

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Alexander Zverev of Germany reacts during his first-round match against Holger Rune of Denmark at the Tennis ATP tournament in Munich, Germany, April 27, 2022. (MATTHIAS SCHRADER / AP)

"I have a lot of respect for him, and I obviously didn't expect to win in two sets, and with a score like this. But it was a really hard match, we played a lot of rallies and I'm really happy about my performance today."

Up next for wildcard Rune, who is seeking his first title on the Tour, is the winner of the second-round meeting between Emil Ruusuvuori and Maxime Cressy.

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Earlier, seventh seed Miomir Kecmanovic overcame local hope Daniel Altmaier 6-2 6-4 to move into the last eight.