'Reaching the semis at all four Slams this season just shows how lucky I've been that I could stay healthy,' said Federer, neglecting to mention that he also carried those semi-final showings forward to titles at the French Open and Wimbledon.

'I always create opportunities, and here again I am in the semis and have a chance to hopefully win the tournament again.'

Nadal, whose day off Friday due to rain may have helped in healing the abdominal muscle pull he's been carrying, is disheartened about scheduling at the event.

Should the four-time French Open winner manage to get to the final and perhaps win his first title at the tournament, he would have to play over three straight days.

Nadal is competing in only his third event since late May, when he was told to rest injured knees by doctors.

'I'm more fresh than last year, 100 percent sure,' said the Spaniard, who played New York a year ago after winning Olympic gold.

'We will see how I am physically (against Del Potro). But last year I was totally destroyed mentally. Mentally this year I am perfect.'

'I think he's a very complete player,' Nadal said of his Argentine opposition. 'In the past, he didn't serve like he is now. He has an unbelievable serve right now and from the baseline, he is very solid.'

Nadal stands 4-2 in the series but has twice lost to the Argentine this season. 'I must play my best tennis if I want to have a chance to win. And that's what I hope to do.'