LOS ANGELES -- Tiger Woods withdrew from the second round of the Genesis Invitational on Friday because of an illness Woods later confirmed to be influenza. 

Woods pulled out of the tournament after hitting his tee shot on the seventh hole at Riviera Country Club. He was taken off the course in a golf cart driven by a tournament official. At one point, Woods put his head in his hands in frustration.

In a social media post Saturday, Woods said that he is "resting and feeling better." 

Rob McNamara, Woods' good friend and the executive vice president of TGR Ventures, said in a statement that Woods began suffering flu-like symptoms Thursday night. On Friday morning, they were worse. He was treated by physicians at Riviera.

"He had a little bit of a fever, and that was better during the warmup," McNamara said. "But then when he got out there and was walking and playing, he started feeling dizzy. Ultimately, the doctors are saying he's got 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."

McNamara said Woods' back, which he had struggled with in Thursday's opening round, was "fine."

"It was all medical illness, dehydration, which is now the symptoms are reversing themselves now that he's had an IV," McNamara said.

After Woods was carted off the course, two fire trucks and an ambulance from the Pacific Palisades Fire Department arrived at Riviera just before 2 p.m. PT after a 911 call was made because no IVs were available on site, sources told ESPN. First responders spent more than 30 minutes inside before exiting and leaving the property.

At 3:43 p.m. PT, Woods exited the men's locker room at Riviera, promptly entered a car driven by his security guard and left the grounds.

Woods battled back spasms in Thursday's opening round and seemed to be having issues with his back again Friday. The 15-time major champion has undergone five back surgeries during his career.

Woods was making his first start in an official PGA Tour event since he withdrew from the rain-delayed third round at the Masters in April. He was 1 over after six holes in the second round Thursday and 2 over for the tournament. The cut ended up being 1 over.

It was a disappointing result for Woods, who was playing in his first official PGA Tour event in more than 10 months, one that he hosts and one that benefits his foundation. As Woods, 48, neared the end of the front nine, a couple hundred fans were waiting for him on the ninth green. He never arrived. After news broke that Woods had withdrawn, fans started heading toward the exits.

Gary Woodland said Woods "didn't look right" before the group even teed off Friday.

"Obviously he wasn't himself," said Woodland, who was paired with Woods and Justin Thomas for the opening two rounds. "It sucks. Everything is better with him there. For him, first tournament back, and he couldn't finish the way he wanted to. That sucks for all of us."

Woodland described Woods as quieter than usual during the second round, even on a day when all three players in the group were trying to make the cut.

"He was definitely trying to fight through it," Woodland said. "I hope he's all right."

The 39-year-old Woodland, who is returning to form after undergoing surgery to treat a brain lesion in September, received a sponsor's exemption from Woods for this year's tournament.

"I wouldn't be here if it wasn't for him," Woodland said. "I hope he gets back. His game looked right. His putting was nice, speed is up for sure. So his game's going to be in a good spot."

It was an all-too-familiar feeling for Woods. Since returning to professional golf after he suffered serious injuries in a car wreck outside Los Angeles in February 2021, Woods has withdrawn or missed the cut in four of his six starts. His two finishes were a tie for 45th in the 2023 Genesis Invitational and a solo 47th in the 2022 Masters.

"My ankle doesn't hurt anymore because no bones are rubbing anymore,'' Woods said Wednesday. "But then again, it's different. Other parts of my body have to take the brunt of it. Just like my back is fused so other parts of my body have taken the brunt of that. I have two different body parts that are now fused. Yeah, other parts of the body have to adapt.''

Friday marked the first time he's pulled out of a tournament before completing 36 holes since the 2019 Northern Trust. It's only the fourth time in his career that he didn't complete at least two rounds in a tournament.

On Thursday, Woods said he hoped to play at least one tournament a month if his body would allow it. The Genesis would presumably be followed by the Players Championship in March, Masters in April, PGA Championship in May, U.S. Open in June and The Open in Scotland in July.

ESPN's Paolo Uggetti contributed to this report.