Andy Murray underwent surgery on his right hip on Monday and said he hopes to be back playing in time for Wimbledon.
The former No 1-ranked Murray, a three-time major winner, has not played a competitive match since a quarterfinal exit at Wimbledon last July.
Murray has been told to expect a 14-week recovery period and he is targeting a return to the court by June.
"I underwent successful right hip surgery at the St Vincent Hospital in Melbourne," Murray wrote on his Facebook page. "I'd like to thank Dr John O'Donnell and all of the staff for looking after me. I look forward to returning to competitive tennis during the grass court season. Thanks to everyone for all the well wishes and support over the last few days. I'll comeback from this."
The 30-year-old Murray, though, accepts he will have to reduce his workload on court.
"I'm certainly not going to be putting in the same amount of tournaments and effort to try to get to No 1," Murray told British media. "I'll certainly be more considered in the amount of tournaments I play, even though I play a conservative schedule anyway in comparison to most of the players on the tour. "I'll be playing a reduced schedule, and then focusing more on trying to win major events and big tournaments rather than trying to achieve certain ranking goals."
Murray said he can get himself back to "95 percent of my best."
"I believe that's enough to compete at the highest level," he added. "No question."
Kerber advances
SYDNEY: Former No 1-ranked Angelique Kerber needed to save two match points before fending off lucie Safarova 6-7 (3), 7-6 (8), 6-2 on Monday to set up a second-round match against Venus Williams.
Kerber, coming off a run to the Hopman Cup final in Perth, overcame two rain delays and a tricky second-set tiebreaker to extend her streak to five straight singles wins. Second-seeded Venus Williams had a bye in the first round.
US Open champion Sloane Stephens lost her first match of the year, beaten 6-3, 6-0 by Italian qualifier Camila Giorgi and is short of match practice ahead of the Australian Open which starts in Melbourne next week.
No 13-ranked Stephens has not won a match since her breakthrough victory over Madison Keys in the US Open final.
The 24-year-old American took a two-month break from tennis after losing her last six matches in 2017 and is now on a seven-match losing streak.
Stephens' exit from Sydney came just one day after French Open champion Jelena Ostapenko was upset 7-6 (3), 6-1 by Ekaterina Makarova on the opening day of the Sydney tournament.
In other first-round matches Monday, former Australian Open finalist Dominika Cibulkova beat No 8-seeded Anastasija Sevastova 6-3, 6-1 and Australia's Ash Barty posted her first win of the summer in a 6-3, 6-4 victory over qualifier Veronica Cepede Royg.
Azarenka withdraws from Oz Open
MElBOURNE: Two-time champion Victoria Azarenka has withdrawn from the Australian Open, with her wildcard entry to the season's first major reallocated to Ajla Tomljanovic.
Australian Open organizers announced Azarenka's withdrawal in a social media post Monday, a week before the tournament begins.
"It's unfortunate that (Azarenka) is unable to travel to Australia this year," organizers posted on Twitter, quoting tournament director Craig Tiley. The Australian Open, "is her favorite tournament and she's looking forward to returning to Melbourne next year."
Azarenka, who won the Australian Open in 2012 and 2013, has been involved in a custody dispute involving her son leo, who was born last December 19.
She hasn't competed anywhere since Wimbledon, where she lost to Simona Halep in the fourth round on July 10.