New York: Roger Federer struggled to hide his disappointment after his bid for a first US Open title since 2008 ended abruptly with a five-set loss to Grigor Dimitrov in the quarter-finals.
The 38-year-old Swiss had defeated Dimitrov in all seven previous meetings but surrendered a two sets to one lead before sliding to a 2-3 defeat.
Federer, a five-time US Open champion, left the court for a private medical timeout to treat his upper back near his neck before the final set but refused to blame injury as the reason for his exit.
"I felt it the whole time. I was able to play with it. My bad not to win," Federer said. "This is Grigor's moment and not my body's moment, so it's OK.
"It's how it goes. I tried my best. By far not too bad to give up or anything. Grigor was able to put me away. I fought with what I had."
Federer was denied on five break points in the 10th game of the fourth set and the 78th-ranked Dimitrov held to force a fifth set, before the Bulgarian broke his rival twice in succession to effectively seal victory.
"Had moments that I was in the lead most of the time. Had a chance to come back in the fourth. Start of the fourth wasn't ideal. Start of the fifth wasn't ideal. That was running behind. That was tough," Federer said.
"Just disappointed it's over because I did feel like I was actually playing really well after a couple of rocky starts.