Sinner says missed double fault derailed him against Tsitsipas
Instead of a double-fault being called, which would have given the Italian a double break, the point played on, with Tsitsipas holding serve for 2-3.
After two more games, Australian Open champion Sinner called for the trainer.
"It's hard to accept it," the Italian second seed said of the call. "I was playing really well at that time."
"Everyone can make a mistake. Afterwards, I had cramps, most likely because of what happened, because it also affects your nerves.
"Your head is spinning, and it's difficult to play. I still tried to do the best I could."