Rune endured his worst sequence of results on the ATP Tour between mid-July and October. The Dane lost 10 of 11 matches at all levels, including the first round of the US Open to Roberto Carballes Baena - a defeat that led him to part ways with French coach Patrick Mouratoglou.
Soon after the French coach departed his camp, Rune's mother made upsetting claims of a clash of egos between Mouratoglou and Lars Christensen, who served as Rune's longtime coach.
Aside from a complicated relationship with his coaches, the 20-year-old had struggled to stay fit in the aforementioned famine period where he lost matches left, right, and center. The strain of playing non-stop tennis affected his back and even retired in the build-up to the US Open in a match in Cincinnati.
Rune eventually made a coaching change, bringing on board Boris Becker, who served as Novak Djokovic's coach between 2014 and 2016. And the effect was almost imminent. In their first tournament together he reached his first semifinal since June and won back-to-back matches on tour for the first time since Wimbledon.
"It is never easy to reverse a negative spiral like the one I went through in the past months. Boris helped me a lot in this. I literally came back from the abyss, from a period in which I was constantly losing matches in the first round."
Rune heaped praise on the German former World No. 1, attributing his improvement to Becker. Rune highlighted one example to show the effect of Becker during a match against Novak Djokovic at the Paris Masters. Rune took Djokovic to his limit once again and reckoned that he would have lost in straight sets just before he made the coaching change.
"If I had played against him [Novak Djokovic] a few weeks ago, I would have lost in two sets. And this is how I played a great game in which I showed that I am close to the maximum. That best shows how far I've come."