Novak Djokovic is 26-0 in Grand Slam matches in 2021.

(AP Photo/Halden Krog, FILE)DOHA – Roger Federer never seriously contemplated retirement while he was away from the tennis tour for more than a year. He did have a hard time dealing with the need for a repeat operation on his bad right knee, though. Obviously I couldn't believe I had to do a second one,” Federer said Sunday ahead of his appearance at the Qatar Open. That knee kept swelling up after bike rides or walks with his four children; he announced in June that he had had a second surgery. I hope, then, by Wimbledon, I’m going to be 100%, and from then on, then the season really starts for me.

Serbia's Novak Djokovic celebrates after defeating France's Jeremy Chardy during their first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Feb. 8, 2021. I really, really appreciate your support in coming out tonight." 7 Aryna Sabalenka, two-time Wimbledon champion Petra Kvitova, French Open winner Iga Swiatek and 2019 U.S. Open champion Bianca Andreescu, returning from 15 months on the sidelines. Playing in her 21st Australian Open, the elder Williams beat Kirsten Flipkens 7-5, 6-2. Two weeks in hard lockdown didn't help 2016 Australian Open winner Angelique Kerber, who lost to Bernarda Pera.

The 10th-seeded Frenchman is a two-time Grand Slam semifinalist, but he can't seem to win anywhere at the moment. ___4:55 p.m.U.S. Open champion Dominic Thiem has moved into the second round at the Australian Open, where he was the runner-up to Novak Djokovic a year ago. Thiem had been 0-3 in Grand Slam finals until emerging for the championship at Flushing Meadows in September. The first tournament of this year’s Grand Slam season began after a three-week delay because of the coronavirus pandemic. Serena Williams begins her latest bid for a 24th Grand Slam singles title in the following match against Laura Siegemund.

There was no certainty until last month that the Australian Open would even be staged. Wimbledon was canceled in 2020, there were no fans permitted at the U.S. Open and very few allowed at Roland Garros. The three-week delay to start the Australian Open this year will mean a slightly different atmosphere — the summer holidays are over, for a start — but that’s unlikely to upset organizers or players. “That’s the first thing I’m looking forward to when I come to Australia, so it was great. Ad“I don’t have a professional tournament back home, so ... every time I come back to Australia, it feels like I’m at home.”___More AP tennis: https://apnews.com/hub/tennis and https://twitter.com/AP_Sports