Holger Rune has opened up on his decision to drop Patrick Mouratoglou from his coaching team last month after he crashed out of the US Open in the first round.

The 20-year-old had been using the facilities at the Mouratoglou Tennis Academy for a while before the Frenchman became his coach. In the past, Mouratoglou has worked with the likes of Serena Williams and Stefanos Tsitsipas, and the 53-year-old was coaching Simona Halep before her suspension due to doping led him to agree to work with Rune.

It was under Mouratoglou's tutelage that Rune won the Stockholm Open before he defeated Novak Djokovic to lift the trophy at the Paris Masters in November last year. This success also helped him to break into the Top 10 of the ATP Ranking for the first time in his career.

However, the Danish player has since been having difficulty getting results on the ATP Tour. He experienced a lot of early exits from tournaments over the summer, which was not helped by a back injury that saw him retire from the Cincinnati Open in the first round.

This came to a head when Rune crashed out of the US Open in his opening match against Roberto Carballes Baena, who defeated the World No. 5 in four sets, 6-3, 4-6, 6-3, 6-2.

As a result, Rune went on to announce his split with Mouratoglou. In a recent interview with Tennis TV ahead of the Shanghai Masters, he explained that the main reason for this was his need for stability and calmness, adding that he felt more comfortable with his longtime coach Lars Christensen.

"I've had ups and downs, and then the coaching situation and everything, but I've had more stability so far, and it's good. I mean, it's important as an athlete, when you have to perform that, everything around you is calm. And I'm trying to do as good as I can.

"I think that I've been with Lars for so many years. And I think he knows me very well and he knows when I'm at my best level. So for him, it's more simple, I think because he knows me this well, than others to be like, I know when you're at your best and how to kind of help you to push to be at the best level, you can be in this.

"We've been having some good practices at home before China, so hopefully. I can get back to my best level," he said.

Unfortunately, Rune's disappointing results have continued so far on the Asian Swing, with a second-round defeat to Grigor Dimitrov at the China Open and a straight-sets loss to Brandon Nakashima in the first round of the Shanghai Masters.