Britain's Andy Murray says he plans to retire after this year's Wimbledon but fears next week's Australian Open could be the final tournament of his career.
The three-time Grand Slam winner, who is struggling to recover from hip surgery, was in tears at a news conference in Melbourne on Friday.
"I'm not sure I'm able to play through the pain for another four or five months," said the 31-year-old Scot.
"I want to get to Wimbledon and stop but I'm not certain I can do that."
However, Murray says he still intends to play his Australian Open first-round match against Spanish 22nd seed Roberto Bautista Agut next week.
The former world number one had surgery on his right hip last January and has played 14 matches since returning to the sport last June.
Murray ended his 2018 season in September to spend time working with rehabilitation expert Bill Knowles but still looked short of the required level when he played world number one Novak Djokovic in an open practice match at Melbourne Park on Thursday.
In his news conference - during which he left the room to compose himself before returning - Murray said: "I'm not feeling good, I've been struggling for a long time.
"I've been in a lot of pain for about 20 months now. I've pretty much done everything I could to try and get my hip feeling better and it hasn't helped loads.
"I'm in a better place than I was six months ago but I'm still in a lot of pain. I can still play to a level, but not a level I have played at."
Murray was frank in his assessment of his abilities, conceding he is no longer able to perform to the level at which he won the US Open in 2012 and Wimbledon in 2013 and 2016.
He told the world's media of the agonising pain he is in when playing and says further hip surgery might be needed to ensure he has a better quality of life in retirement.
"The pain is too much really," said Murray, who is also a two-time Olympic champion. "I need to have an end point because I'm playing with no idea of when the pain will stop.
"I'd like to play until Wimbledon - that's where I'd like to stop playing - but I'm not certain I'm able to do that."
Speaking to BBC Sport, he added: "A second surgery is an option. I wouldn't be taking the option to have a surgery to resurface and replace my hip with the view to playing at the highest level again. The number one reason to have something so serious is improve your quality of life and being in less pain.
"Athletes have had operations like that done and come back to play - but certainly not in tennis and in singles.
"If I do that I'm not sure I will be competing again."