Roger Federer said Sunday he's not sure whether he'll be ready to return from a knee injury by the time the 2021 Australian Open starts Feb. 8.

"I would have hoped that I would be at 100 percent by October," Federer said, per Swiss outlet SRF (via ESPN's D'Arcy Maine). "But I still am not [100 percent] today. It will be tight for the Australian Open. I wish I was further along, but at the same time I'm satisfied with where I am at the moment."

The 20-time major champion hasn't played since the 2020 Australian Open in January when he reached the semifinals before losing to eventual champion Novak Djokovic.

Federer, 39, underwent surgery on his right knee in February and, after an initial timetable that suggested he could return by the summer, he ended up missing the remainder of the year.

He explained Sunday he remains optimistic about the future but admitted there's a chance he won't be able to return to the court, per SRF.

"I stand here tonight with an incredibly good feeling and share that with all of you," Federer said. "I hope that there will be something to see with me next year. If not, then that's an unbelievable end point."

The Australian Open was delayed three weeks because of COVID-19 concerns with players likely having to travel to the country 14 days before the event for quarantine, per ESPN.

If Federer isn't ready to play in the tournament, the next major isn't until the French Open in May. Wimbledon in late June, the Olympics in July and the U.S. Open in late August are the other high-profile events on next year's schedule.

Federer's most recent Grand Slam title came in the 2018 Australian Open.