Stefanos Tsitsipas confronted his opponent after losing at US Open

Stefanos Tsitsipas was eliminated from the U.S. Open on Thursday in a major upset, and he was openly unhappy with his opponent after the match.

Tsitsipas lost to Daniel Altmaier in the second round of the U.S. Open at the USTA Billie Jean King National Tennis Center in Queens, N.Y. Tsitsipas won two of the first three sets before losing 7-6 (5), 1-6, 4-6, 6-3, 7-5.

When Tsitsipas and Altmaier went to shake hands after the match, it quickly became clear that Tsitsipas was angry over something. He could be heard telling Altmaier, “Next time don’t wonder why I hit you, OK?”

Altmaier initially seemed to brush the comment off, but Tsitsipas elaborated.

“No, I’m just saying, if you serve underarm…” Tsitsipas added as Altmaier walked away.

Stefanos Tsitsipas had some words with Dan Altmaier after losing to him at U.S. Open:

He’s complaining about Dan hitting an underarm serve during the 4th set.

Frosty. 🥶

pic.twitter.com/eEaPIpuApL

— The Tennis Letter (@TheTennisLetter) August 29, 2025

According to Reuters, Altmaier used an underhand serve multiple times as he rallied during the fourth set to beat Tsitsipas. The serve was legal but did not sit well with Tsitsipas.

Tsitsipas suggested that he deliberately tried to hit Altmaier with the ball during the match because Tsitsipas was trying to send a message about the underhand serves.

Altmaier told reporters after the match that he thinks Tsitsipas will regret the actions.

“Tomorrow Stefanos will regret his words. In football, fists fly or people get into arguments. In tennis, you say something that might not be appropriate,” Altmaier said. “That’s part of the sport. A lot of money and self-confidence are at stake. When you’re playing tennis until midnight, you can sometimes say something you don’t really mean. Or maybe he does.”

Tsitsipas, who has gotten away with some controversial moves at grand slam events himself, was at one point ranked the No. 3 player in the world. The former Australian Open and French Open finalist has struggled this year and has not won back-to-back matches since April.