Stefanos Tsitsipas confronts Daniel Altmaier in heated moment after US Open loss

Tsitsipas was unhappy with Altmaier’s underarm serving after crashing out of the US Open in the second round

Daniel Altmaier and Stefanos Tsitsipas argue after shaking hands at the net (AFP via Getty Images)

Stefanos Tsitsipas confronted Daniel Altmaier and expressed his disapproval at his opponent’s underarm serving after a five-set defeat to the German in the US Open second round.

Tsitsipas had a match point towards the end of the fifth set but could not take it as Altmaier prevailed, winning 7-6(5) 1-6 4-6 6-3 7-5 in a tough contest that lasted over four hours.

The result continued Tsitsipas’ poor run of form, with the two-time grand slam finalist failing to advance past the second round of a major this season after first-round exits at the Australian Open and Wimbledon.

Tsitsipas approach Altmaier at the net before his opponent walked away (AP)

Altmaier fell to his back after winning match point and there was an intense handshake at the net as Tsitsipas said to his opponent: "Next time don't wonder why I hit you, ok?”

It referred to a moment earlier in the match where Tsitsipas had aimed a forehand at Altmaier’s body as the German came into the net, with Tsitsipas then holding up his hands in apology.

Altmaier did not respond to Tsitsipas’ comment so the Greek continued: “I'm just saying if you serve underarm... if you serve underarm.” Altmaier then walked away while shaking his head.

Tsitsipas, a former World No 3, has just one win in his last seven matches - including his first-round retirement from Wimbledon last month. He had reappointed his father, Apostolos Tsitsipas, as his coach shortly before the US Open.

World No 56 Altmaier is into the US Open third round for the first time and will face Australian eighth seed Alex de Minaur.