Britain's Andy Murray said it would be "naive" and "silly" to think he will ever return to his "very best" following hip surgery.
Murray, 32, has mainly competed in doubles matches this year, and is now playing "pain-free" following career-saving treatment in January.
The three-time Grand Slam champion continues his singles comeback at the Zhuhai Championships in China.
"I'm not expecting to get back to my very best," he said.
"I think it would be probably a bit naive and silly to think that would be the case.
"I do feel like tennis-wise I can still compete at the highest level in terms of my skill, it's just whether physically I can get to a high enough level to be competitive right at the top."
The Scot faces world number 72 Tennys Sandgren in the first round in Guangdong on Tuesday - the first of three tournaments in China in as many weeks - as he steps up his bid to recapture his singles form.
The former world number one, now ranked 413th, admits he still has "quite a way to go" but is "enjoying" his comeback and if he "stops improving" he will make a call on his future.
Murray, who made the quarter-finals of the Cincinnati Masters doubles with partner Feliciano Lopez last month, added: "Tennis has always been a huge part of my life, but I realised that actually my health was the most important thing for a happy life and I had always been worried about what life might look like after tennis, but now I'm not worried.
"I had a glimpse these last few months and it was brilliant - hanging out with friends and family, and it was great. "
After Zhuhai, Murray is set to compete in the China Open in Beijing and the Shanghai Masters, before he returns to Europe to take part in the European Open in Antwerp, which begins on 13 October.