Stefanos Tsitsipas has parted ways with his father as his tennis coach, one day after lashing out at him following a stunning defeat at the National Bank Open in Montreal.

Tsitsipas, the No. 11 player in the world, was upset by Japanese player Kei Nishikori, ranked 576th in the world, in straight sets in the first round of the ATP Tour tournament on Thursday.

During the match, Tsitsipas, 25, argued with his father, Apostolos Tsitsipas, and afterward, went on a tirade about him during media availability.

“I need and I deserve a coach that listens to me and hears my feedback as a player,” Tsitsipas told reporters after detailing a disagreement he’d had with his father about changes in his racquet strings. “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.”

Friday, Tsitsipas announced his father would no longer be his coach.

“It is with a heavy heart that I inform you that my collaboration with my father as a coach has come to an end. I prefer to keep my father in his role as a father, and only as a father,” Tsitsipas wrote on X.

He continued to say that as an “introvert,” he let his frustrations simmer until they bubbled over, and that he regretted his actions.

“My behavior on the pitch was unacceptable, and I feel disappointed that I got to a point where I showed a dark side of myself. When I feel disrespected, judged, or emotionally attacked, I tend to lose control of what comes out of my mouth, which goes against my values ​​as a human being. I lost control and could not see clearly in front of me,” Tsitsipas continued.

“My father has been trying for the last few years to train me, raise me the right way and provide me with knowledge and wisdom, both on and off the field. I thank him for that. I thank him for the sacrifices, pain and suffering he has endured to make this endeavor a success. From now on, his role will remain within the confines of the father role, and that alone.”

Tsitsipas said that his father would continue to travel with him, and that he did not have the replacement coach in mind.

The match on Thursday was Tsitsipas’ first since losing to eventual gold medalist Novak Djokovic in the quarterfinals of the Olympics.