Tennis star Stefanos Tsitsipas has torn into his father after being upset by Kei Nishikori on the ATP tour in Canada.

The Greek was looking to bounce back from his quarter-final defeat by eventual winner Novak Djokovic in the quarter-final of the men's singles in the Olympics in Paris.

He was competing in the last-32 of the men's singles, but lost in straight sets to the Japanese star, going down 6-4, 6-4 in Montreal.

After, he launched a staggering outburst against his father - who is also his coach - Apostolos Tsitsipas, threatening to change his coach because of the way he said he has been treated.

The 34-year-old seemed to accuse his father of not hitting the standards he is looking for, suggesting that the player needs to have more of a role in what is happening during sessions and games than the coach.

'I need and I deserve a coach that listens to me and hears my feedback as a player,' he said in his post-match outburst on Thursday. '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.'

Stefanos, who is ranked No 11 in the world, has suffered a number of shock defeats in recent weeks, including against Nishikori, who is ranked No 286 in the world.

At Wimbledon, he lost against Emil Ruusuvuori, who is ranked No 70, in the second round.

He could now lookto change his coach ahead of the US Open, which will start in September.

Apostolos has coached his son on and off since his childhood, but they have clashed before, including when Mark Philippoussis was briefly brought into the 25-year-old's team.

Stefanos has also clashed with his mother, Julia Apostoli, before, as she criticised her son's relationship with fellow tennis star Paula Badosa.

All four of Apostolos' sons play tennis, though Stefanos is the best.

Apostolos has gained a reputation for being loud on the court between most points, with Stefanos seemingly losing patience on the back of his defeat in Canada.

In January 2023, he was slammed by tennis fans for refusing to stand during the award ceremony after his son lost the Australian Open final to Djokovic.

The Greek star's dad was seen sitting stony-faced while the rest of his son's team stood and applauded during the players' speeches and trophy presentations, as is traditional after a final.

Apostolos remained seated and didn't clap during Stefanos' classy post-match remarks.