A downbeat Woods, who turns 40 on December 30, appeared before the media on the eve of the Hero World Challenge, the 18-man tournament hosted by his foundation, to announce he does not have a timescale for his return.
Woods said he has not been able to begin rehabilitation work for the two back operations he has had since his last start over three months ago.
Asked about his return, he said: "I have no answer for that. Neither does my surgeon or my physio. There is no timetable.
"There is nothing I can look forward to, nothing I can build towards.
"Where is the light at the end of the tunnel? I don't know."
Woods's comments have led to speculation that his glittering career may be coming to an end, but he has received words of support from world No 3 McIlroy.
The Northern Irishman posted a photo of the pair together on Instagram, along with the words: "Wishing my idol and friend a speedy recovery. Golf without him doesn't bear thinking about. Hope to see you back on the course soon @tigerwoods."
Woods, who revealed video games have been one of his main pastimes, insists his hope is to resume his career and "get after it with these guys".
But he also acknowledged that any good golf from now on would be "gravy" on top of a career that saw him ranked No 1 in the world for 623 weeks.
"I think pretty much everything beyond this will be gravy," he said. "If that's all it entails, then I've had a pretty good run."
Now ranked down at 400, Woods continued: "It's just taking it literally day by day and week by week and time by time.
"It's different from any of the other surgeries and procedures that I've had in the past, where, okay, you blow out your ACL, which I did and I had ACL reconstruction and okay, you're back in nine months. That's the timetable.
"For nerves, there are really no timetables, and therein lies the tricky part because you can come back earlier or you can come back later.
"It just depends on how the nerve heals and how it settles.
"I listen to my surgeon, I listen to my physios, and we just take it day by day.
"Hopefully the day by day adds up to something positive here soon."
Woods said his decision to become a vice-captain for Davis Love III on the 2016 US Ryder Cup team was not related to his playing future, whatever that might be.
Referring to the Americans' response to the 2014 Ryder Cup defeat to Europe at Gleneagles, he said: "When I was asked to be part of the task force and I committed to that, all the guys on the conference call, they all know what my feelings were about the Ryder Cup and how I wanted to be a part of it.
"I told Davis, 'whatever you want me to do, I'll do'."