Federer unconcerned by mounting injury toll

"The guys who are hurt lately, it's mostly because they are 30-plus," 36-year-old Federer said during a press conference on Saturday ahead of the U.S. Open, which kicks off on Monday.

"I don't think there needs to be that much addressing because the players, they have the option not to play as much as sometimes they have to or want to."

"I don't think the tour is doing much wrong, to be quite honest," he said of the ATP schedule, which runs from January to November.

Federer made his comments a few hours before world number two Andy Murray announced he was pulling out of the tournament due to the hip injury that hampered him during his unsuccessful defence of his Wimbledon title in July.

Thirty-year-old Murray joins 12-times grand slam winner Novak Djokovic and 2016 U.S. Open champion Stan Wawrinka in missing the tournament through injury.

Djokovic, also 30, is suffering from a bad elbow and 32-year-old Wawrinka is dealing with a long-term knee problem.

Federer said the absence of some of the sport's top players created an opening for lesser-known talent to emerge.

"It's a huge opportunity for guys ranked outside of the top 10 because there are less guys to beat, getting to quarters or semis, potentially, depending on your section," he said.

The world number three, who has won both the Australian Open and Wimbledon in 2017, said he had recovered from the back complaint that forced him to withdraw from the Cincinnati Masters earlier this month.

"I have been playing sets the last few days and I'm really happy how I'm feeling ... few days out of the first round here now," he said.

Federer is scheduled to face 19-year-old American Frances Tiafoe in the first round of the tournament, which runs until September 10.