Djokovic ended a two-year grand-slam drought at Wimbledon last month to win one of tennis' big-four tournaments for the 13th time.

The 31 year-old has been installed as favourite in New York by some bookmakers, with Rafael Nadal and Federer not far behind.

Federer is excited to see Djokovic return to form but does not know how the added pressure from his Wimbledon win will affect his rival.

Addressing the media before his Cincinnati Masters campaign, the Swiss star said: "Novak can play with less pressure again I guess, to some extent, but you can always get caught up in the pressure, the media saying 'well clearly now you're going to win the US Open', and you're like 'well, I guess so, yes'.

"And then rather than you being able to say 'well, we'll see what happens', perspective changes from your side but also from the media.

"But it's definitely exciting times, a lot of the best players are back in the game and I think the US Open is going to be epic.

"Novak winning Wimbledon, obviously that was massive, I don't think he expected it.

"I remember the press conference he gave [after losing to Marco Cecchinato] in Paris when he was like 'I don't know yet, I was frustrated, I just want to get out of here'.

"And people were asking him 'what, you're not going to play the grass?' And then he should have won Queens and goes on to win Wimbledon, so things can turn very quickly, regardless if you're positive or not.

"Sometimes when you just put yourself out there and then you get excited in a quarters or semis of a slam you can start playing your best tennis.

"I thought it [Djokovic winning Wimbledon] was great for the sport, I'm happy for him because I know it probably it hasn't been easy the last couple of years for him but then again I don't think anybody should be feeling sorry for him, like people feeling sorry for me or Rafa, we've had so much success that it's just more beautiful when you do come back after a tough time."