Roger Federer is no longer in the mix for the title at the US Open after being dumped out by Juan Martin del Potro in the quarter-finals on Wednesday (6 September) but gave his views on the upcoming semi-final clash between his conqueror and Rafael Nadal on Friday.

The Spaniard will be installed as the favourite to win his second Grand Slam of the year after the Swiss ace was knocked out, but is certain to face stiff competition for a place in the final from Del Potro, who seems re-energised after snatching victory despite being two sets down against Dominic Thiem and then beating Federer in four sets.

Nadal has looked sharp since the start of the tournament and has dropped just two sets on his way to the semi-final. He dominated young Andrey Rublev in the quarter-finals and will be in a confident mood going into the last four clash against Del Potro.

The Argentine, on the other hand, started the tournament strong with straight-set wins in his first three matches, but then found himself two sets down against Thiem. Del Potro made a remarkable comeback winning the next three sets to take momentum into this game against Federer, which he dominated for most parts before causing the biggest upset of the tournament.

Del Potro is facing Nadal for the first time at the US Open since 2009 when he beat the Spaniard in the semi-finals on the way to the title.

The 15-time men's singles Grand Slam champion leads the head-to-head record 8-5 but the Argentine has won their last two encounters – at the Olympics last year and the Shanghai Masters in 2013.

"I think it's going to be an exciting match, you know," Federer said, as quoted by the Metro. "Both are great shot makers. They have, you know, some of the best forehands in the game. They are both winners. They know how to get it done. I think it should been an exciting semi."

"Yeah, I mean, Rafa now is playing within himself a lot. I think he was very focused here, in practice and also in the matches. I assume we know what we're going to get from him.

"Juan Martin, I hope he recovers, you know. It's big for him now to have a day rest tomorrow, because again, it's an emotional night and all that stuff. Rallies weren't very long, so he did well to bounce back from his Thiem match, you know. That was nice for him," the Swiss ace added about Del Potro's chances.

Rafael Nadal
Rafael Nadal and Del Potro last played in the semi-finals of the 2016 Olympics when the Argentine won Getty

The 2017 US Open has been a tournament of upsets with a number of seeded players falling in the early rounds. There were only nine of the 32 seeded men's singles players left going into the fourth round of the event.

The high rate of attrition among seeded players will now ensure a first time Grand Slam finalist from the bottom half with Spain's Pablo Carreno Busta and South Africa's Kevin Anderson contesting the other semi-final. The former is favourite and Federer believes that he has had the easiest run in the entire tournament.

Carreno Busta, the 12th seed, played qualifiers in his first four rounds before coming up against 29th seed David Schwartzman in the quarter-finals, whom he dispatched in straight sets. He now awaits Anderson, who came through in four sets against Sam Querrey.

"I mean, in a way it's been a struggle for everybody here, except maybe Carreno Busta,' the 19-time emen's singles Grand Slam champion said, as quoted by the Metro. "He's just been cruising."

"The rest of us have all been fighting something, you know. I'm sure other players are fighting injuries, you know, but they're not talking about it. I unfortunately had to because of the Montreal and Cincinnati situation. Otherwise I wouldn't have talked about it, either," Federer added revealing that he had still not fully recovered from the back injury he sustained in the final of the Rogers Cup.

Pablo Carreno Busta
Pablo Carreno Busta will take on Kevin Anderson for a place in the final of the 2017 US Open Getty