In an interview to Eurosport, the former world No. 2 Alex Corretja commented on Novak Djokovic, Roger Federer and Rafael Nadal all playing just one tournament prior to the US Open. Corretja said: "After Wimbledon, as we all know, he took a time off, so the preparation to go to Montreal was a right one.
Once he got those matches, and especially winning in Montreal, I think skipping a tournament was correct because he took the rhythm he needs to, he has the confidence and he is now ready for the Open and with a week before practicing and in the first matches he will get the rhythm he needed to win the title again if he can.
Novak instead did not play the first tournament and he instead played in Cincinnati and reached the semifinals. This kind of players doesn't need to play a lot because they ready for the Majors and the summer can be very long, so you cannot play in Washington, you cannot play until Montreal and then in Cinci because you get into the US Open being destroyed.
Both Novak and Federer, who only played two matches, will be ready. I think like in the Australian Open, Wimbledon and French Open, Djokovic, Federer and Nadal will be above the others and then you have to wait for someone who is going through his best time.
You are waiting for the likes of Stefanos Tsitsipas and Karen Khachanov, or Alexander Zverev or Roberto Bautista Agut who is doing very well too. But they are not the favorites. They can play a great tournament, but I am not sure they are ready to win a Major.
For Nadal, it will mostly depend on the draw because it's not like French Open where he is the favorite regardless of anything."