Stefanos Tsitsipas has slammed his father's coaching style after suffering a shock straight-sets defeat at the Canadian Open on Thursday.

The 25-year-old was beaten 6-4 6-4 by Kei Nishikori, the world number 576, as he secured the scalp of the tournament so far in Montreal.

It follows a disappointing Olympic Games for Tsitsipas, who was knocked out by eventual winner Novak Djokovic in the quarter-finals.

He also struggled at Wimbledon last month, suffering defeat to Emil Ruusuvuori in the second round.

Now, he has hit out at his coach and father, Apostolos Tsitsipas, who he asked to leave midway through Thursday's match, for seemingly not reaching the standards he is looking for.

"I need, and I deserve, a coach that listens to me and hears my feedback as a player," Tsitsipas said.

"My father hasn't been very smart or very good at handling those situations. It's not the first time he has done that. I'm really disappointed at him.

"I really don't know right now if I'd consider any changes, but I'm really disappointed.

"The most important thing for a player is to have direct and good feedback from a coach. The coach is not the one holding a racket. The player is the one trying to execute a game plan.

"It's a collaborative work that you put in together. It has to be reciprocal in order for me to try to develop my tennis. It's something I don't want to get stuck at that."