Roger Federer suffered a defeat against Juan Martin del Potro in the US Open quarter-finals, meaning he and Rafael Nadal once again will not be meeting each other in this tournament.

Federer entered the tournament with some back issues, which disturbed his preparation and caused him troubles in the first two rounds.

It was a slow start for the Swiss. He had to come through two five-setters in his clashes with Frances Tiafoe and Mikhail Youzhny in his opening two matches.

Federer then showed signs of finding his form against Feliciano Lopez and Philipp Kohlschreiber in the third and fourth rounds, but he was not consistent enough against Del Potro in the quarter-finals and suffered a defeat 5-7, 6-3, 6-7, 4-6 .

The maestro admits he was second best in the match, and feels he was rightly eliminated after failing to produce his best performances throughout the tournament. 

"I need to recover, go back to practice courts, and come back strong for the end of the season," he said after his defeat against the 24th seed.

Federer feels he was not that bad throughout the tournament, but insists Juan Martin del Potro’s semi against Rafael Nadal will be worth watching.

"I played okay in this tournament, but I know I can be better. Rafa and DelPo will be a great match, both have killer forehands.

"I can play better, but worse too, I knew going in I was not in a safe place, I’m out of the tournament and rightfully so.

"I didn’t even think about it, as I lost that match, that (a semi-final with Nadal) is not going to happen. I’m dealing with just trying to understand what happened and just to overcome this in the next few hours, days, weeks."

Federer remained classy as usual in his comments and although he admits he was not at his best, the Swiss pays tribute to Del Potro's merit.

"Of course it is a pity, but Juan Martin deserves it more.

"I feel I have no place in the semis and he will have a better chance to beat Rafa, to be honest. The way I played or playing right now, it’s not good enough in my opinion to win this tournament.

"It’s better I’m out and somebody else gets a chance to do better than me."