Stefanos Tsitsipas' dismal run of form continued with a second round exit at the US Open, and the Greek added to a drama-packed first week of the tournament with his reaction to the loss.
The two-time Grand Slam runner-up fell 6-7(5), 6-1, 6-4, 3-6, 5-7 to world No 56 Daniel Altmaier on Grandstand court on Thursday night at Flushing Meadows.
While Tsitispas losing the four-hour-and-26-minute battle was an upset on paper, it was not much of a surprise given the 27-year-old's struggles. The former world No 3, who is currently ranked 28th, has not won back-to-back matches since the Barcelona Open in April.
Altmaier hit an underarm serve during the fourth set, which he battled back to win after losing his serve in the opening game.
The 26-year-old German also saved a match point when serving at 4-5, 30-40 in the fifth set before earning the decisive breakthrough on Tsitsipas' serve in the following game.
After Altmaier served out the match, he was confronted by a visibly frustrated Tsitsipas during the handshake for using an underarm serve.
Tsitsipas said he would hit the ball at Altmaier if the German served underarm against him in the future.
"Next time, don't wonder why I hit you, ok? No, I'm just saying, if you serve underarm... if you serve underarm," said the Greek.
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Altmaier looked taken aback by Tsitsipas' comments and walked away to de-escalate the situation.
In an interview with Sky Sports, Altmaier said: "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. 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. I respected that."
Speaking to Bounces, the German added: "I know that sometimes in the heat of the moment, you can say stuff you don't normally would like to say. You regret afterwards. So I think we all know about these discussions at the net; I'm not a fan of it.
"Even if I would have lost, I would not enter discussions because it's just, like, the heat of the moment.
"You need to cool down; let's see if he reacts to it or sticks to his opinion. Which is fine for me. I know what I did and that's it. It's part of the game."