Roger Federer will miss the Australian Open in January and isn't likely to return to competition until mid-2022 as he recovers from multiple knee surgeries, the former world No 1 says.
Federer (40) also said he would be "extremely surprised" if he was able to play at Wimbledon, a Grand Slam he has won a record eight times with his last title coming in 2017.
The 20-times Grand Slam champion said he would be able to resume running in January and return to training on the court in March or April.
"I need to be very patient and give my knee the time to heal. The next few months will be crucial," Federer said in an interview carried by several Swiss media outlets on Wednesday.
Federer's agent did not immediately respond to a request for comment.
Federer is tied with Spain's Rafa Nadal and Serbian Novak Djokovic in the race to be the most successful men's singles Grand Slam champion of all time.
His coach Ivan Ljubicic had said earlier this week that Federer was unlikely to play at Melbourne Park in January as he was not going to be at 100%.
He withdrew from the French Open in June after winning his third-round match to save himself for Wimbledon but fell at the quarter-finals hurdle at the grass court Grand Slam a month shy of his 40th birthday.
Another injury forced Federer to skip the US Open as he went under the knife again and he said doctors also fixed cartilage in his knee.
"This summer it was decided to suture the lesion to my meniscus, which involves some downtime," he said.
"The doctors took the opportunity to also treat my cartilage. The combination of these two procedures requires patience and caution."
Federer has not won a Grand Slam since clinching the Australian Open title in 2018 but the Swiss veteran said he is still holding out for a 'miracle'.
"My life is not going to collapse if I don't play a Grand Slam final again.
"But it would be the ultimate dream to go back. And in fact, I still believe in it. I believe in these kinds of miracles."
Federer very important for sport - Djokovic
World No 1 Djokovic says he hopes Federer would return to competitive action soon and be able to compete with the best again.
"Roger is an icon of our sport and people around the world love him. They love watching him play, love seeing him around," Djokovic said after securing a semi-final spot at the ATP Finals with a 6-3 6-2 victory over Russian Andrey Rublev on Wednesday.
"He's very important for our sport on and off the court. For the sake of our sport, I sincerely hope that we can see him play at least another time. I'm sure he doesn't want to end his career this way.
"I think he's going to definitely give it a last push, a last try. For everything he has achieved and created for this sport, he deserves to play and deserves to have a proper farewell."
Djokovic is looking to match Federer's record of six titles at the season-ending ATP Finals. He is top of the Green Group standings with two wins from two matches and will face Britain's Cameron Norrie in his final group game on Friday.
