American great John McEnroe expects Roger Federer's sensational comeback season to continue in New York when the U.S. Open kicks off next week.
Since returning from a six-month hiatus in January, the 36-year-old Swiss has been in stupendous form as he has won five titles, including the Australian Open and Wimbledon.
"At the moment we're just assuming that Roger is going to pull the rabbit out of the hat again," four-times U.S. Open champion McEnroe said at a pre-tournament media conference.
"If Roger wins this, it will be one of the great stories in that last 50 years or ever."
"I saw him today and I said, 'I've got to tell you, hats off. I've watched tennis for 40 or 50 years and I've never seen anything like this'."
One question mark hanging over Federer is his health.
Back pain appeared to limit his mobility during the Rogers Cup final in Montreal earlier this month, where he fell in straight sets to 20-year-old German Alexander Zverev.
It was only the third time Federer had lost a match this year and as a result the 19-times grand slam champion opted to skip the Cincinnati Masters to tend to the injury.
Federer will need to be at 100 percent to compete at Flushing Meadows in the gruelling best-of-five-set tournament, where scorching heat and suffocating humidity are the norm.
Apart from Federer, world number one Rafael Nadal and Briton Andy Murray, who is coming back from a hip injury that forced him to skip all the hardcourt tournaments in the run up to the Open, are the names in the mix as potential winners of the final major of the season.
If those favorites falter, the tournament is up for grabs, McEnroe said.
"It wouldn't be shocking considering that Roger is 36 and he's had two majors already so perhaps things don't go as smoothly as they did the other times. And let's say Nadal wasn't around and Murray wasn't healthy, then it's like, who is going to do it?"