Tiger Woods was put on an IV drip after pulling out of the Genesis Invitational on Friday just six holes into his second round.
The 48-year-old was making his first competitive appearance of 2024 in Los Angeles but was forced to withdraw due to illness.
Woods carded a +1 round of 72 on Thursday and caused some concerns over his fitness after revealing he had a back spasm on the 18th hole.
He played down the issue and was fit to return for Friday's action, starting his second round with a birdie on the first hole.
Tiger Woods withdrew from the Genesis Invitational on Friday
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However, he hit back-to-back bogeys on the fourth and fifth, before withdrawing after striking his tee shot onto the seventh fairway.
Woods was seen in visible discomfort and was driven back to the clubhouse, at one moment putting his head in his hands.
It is yet more frustration for the 15-time major champion, who was making just his seventh appearance at an official PGA Tour event since November 2020.
Woods has had a string of injury and fitness issues in recent years and pulled out of the Masters last year due to an ankle problem.
He underwent surgery on the issue and didn't return until the Hero World Challenge in December, where he finished 18th.
Woods confirmed he would play a limited schedule in 2024, likely just one tournament a month, so the latest withdrawal will come as a big disappointment.
Rob McNamara, Woods' long-term business partner, confirmed Woods was suffering from flu-like symptoms but was feeling better after being put on an IV drip.
McNamara said: "So he started feeling some flu-like symptoms last night. Woke up this morning, they were worse than the night previous.
"He had a little bit of a fever and that was better during the warm-up but then when he got out there, and was walking and playing, he started feeling dizzy.
"Ultimately the doctors are saying he's got some - potentially some type of flu and that he was dehydrated.
"He's been treated with an IV bag and he's doing much, much better.
"Not physical at all, his back's fine. It was all medical illness, dehydration, which is now the symptoms are reversing themselves now that he's had an IV."
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Tiger Woods looked in visible discomfort as he was driven away from the course
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Woods hosts the Genesis Invitational in Los Angeles and it remains to be seen whether he will return to the tournament this weekend to carry out those duties.
USA star Patrick Cantlay holds a five-shot lead after carding a round of 65 on Friday.
Former PGA Championship winner Rich Beem noticed all was not well with Woods during the first few holes of his second round.
Beem said: "When he was walking off the fourth green, he took a couple of steps and stopped and composed himself before he carried on walking down to the fifth tee box.
"When he did, once he got down there, he leaned up against a cooler and he was visibly in pain.
Tiger Woods left the course early after withdrawing from the Genesis Invitational
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"There was a lot of commotion on the fifth green and behind the sixth green with PGA Tour security, Tiger's staff and whatnot, so you knew something was up.
"Once he hit the tee shot on seventh I thought he might continue, but he couldn't. He apparently wasn't feeling very good before the round began and as he was walking around here, it just wasn't getting better.
"I don't think it was so much physical, it was that he was just feeling sick to his stomach. I don't think he had a very good night last night, from what I'm reading between the lines.
"It might not be as much physical with the legs as it is just feeling more under the weather."