Federer has won 20 Grand Slam titles across the course of his career but his form has curtailed as of late with a disappointing quarter-final exit at Wimbledon and a loss in the Cincinnati Masters final.
In the meantime, Nadal has won the Rogers Cup and Djokovic claimed both Wimbledon and the Cincinnati Masters.
The Serbian has been installed as the early favourite to win the final Grand Slam of the year.
And seven-time major winner Wilander believes it will be either Nadal or Djokovic who scoops the New York prize.
“Novak Djokovic and Rafael Nadal are of course the biggest favourites,” Wilander told Eurosport.
“I’m not sure you can put Roger Federer together with the two.
“When I watch Novak play nowadays, I do not think he plays the same as before, it’s something different.
“Outside the court, he seems very humble and relaxed, but he gets very driven as soon as he is back on the track.
“Novak is favourite, but he has Rafael.”
Alexander Zverev, 21, is widely regarded to be the next star of tennis.
However, the German’s record at Grand Slams is terrible, having only reached the last eight on one occasion.
And Wilander believes Zverev is still not ready to reach the latter stages of the US Open, although he has named two other NextGen candidates who could cause a stir.
“At the moment, it does not seem like Alexander Zverev will be,” Wilander added.
“I think it might be Stefanos Tsitsipas or Denis Shapovalov who can break through and get to the quarter-finals or semi-final.
“Andrey Rublev went to quarter-finals last year and I do not know if you can call it breakthrough.
“I think you need to go to semi-final or final to call it a breakthrough. But I think Tsitsipas and absolute Denis Shapovalov have the game.”