With the U.S. Open still scheduled to go ahead in August, one of the most interesting questions for tennis fans about the tournament is whether Roger Federer can win the ‘Race to 21’ Grand Slam titles and win his first final at Flushing Meadows since 2008.

Rusedski, in an interview with Tennis365, said that while many have joked that the current crisis is a help to Federer’s recovery from injury, the serious question is whether the ‘Fed Express’ will be able to go through the gears once he’s back on court.

“I think it’s going to be pretty difficult for him to challenge for the Grand Slams when we start again,” said Rusedski “He will be 39 by then and winning major titles at that age will be very tough.”

Backing up Rusedski’s remarks about Federer’s physical capabilities, the Swiss former world number one hasn’t won at Flushing Meadow in 12 years, longer than many would credit given his former dominance of the event, with five years of consecutive victories between 2004 and 2008. In those five consecutive wins, he beat five different men in the finals: Lleyton Hewitt, Andre Agassi, Andy Roddick, Novak Djokovic and Andy Murray. In fact, since Federer last won it, he has only reached the U.S. Open final twice, losing to Juan Martin Del Potro in 2009 and Djokovic in 2015.