Grigor Dimitrov of Bulgaria reacts to his win against Roger Federer of Switzerland in their Men's Singles Quarter-finals tennis match during the 2019 US Open at the USTA Billie Jean King National Tennis Center in New York on September 3, 2019. (Photo by DOMINICK REUTER / AFP) (Photo credit should read DOMINICK REUTER/AFP/Getty Images)

Roger Federer did not blame his upper-back injury for the defeat, as Grigor Dimitrov won a gruelling five-set encounter, 3-6 6-4 3-6 6-4 6-2 at the US Open.

Despite a fast 3-0 in 30 minutes start in the first set, Federer slowed down after that, eventually requiring medical assistance after the fourth set.

“I just needed some treatment on my upper — back, neck,” Federer said.

”Just needed to try to loosen it up, crack it and see if it was going to be better but this is Grigor’s moment and not my body’s moment, so … It’s okay.”

The Bulgarian put the early pressure on Federer at the start of the fifth and final set by  breaking the 3rd seed's serve then holding his own, therefore starting the set 2-0.

Federer was unable to recover the set, therefore going down 6-2 in the fifth.

After a disappointing 2019 season and sliding down a 78th ranking, Dimitrov has reclaimed his form.

He will play Russian 5th seed, Daniil Medvedev in a couple of days time in a semi-final.