The road to the Masters got off to a bumpy start for Tiger Woods when he withdrew from the Honda Classic with what he said was a lower back injury.

Woods was five-over par for the final round when he shook hands with Luke Guthrie on the 13th green and told him he was finished. It was the farthest point at PGA National, and the tournament sent a van to collect Woods and his family.

Police kept the media from the car park.

"He just came over and said, 'I can't go anymore. It was a pleasure playing with you,"' said Guthrie, who was paired with Woods the past two days. "I just said, 'Take it easy. Feel better.' Pretty uneventful."

American Russell Henley won with a birdie at the first hole of a four-way play-off, denying Rory McIlroy in a tournament he had led for three rounds.

enley rolled in his birdie putt at the par-five 18th for the victory after Northern Ireland's two-time major champion McIlroy, Scotland's Russell Knox and American Ryan Palmer had all parred the par-five that served as the decider.

The speculation over Woods' future is bound to grow in the run-up to the Masters next month.

Woods said through spokesman Glenn Greenspan it was a lower back problem that had started on Sunday morning as he was warming up. He was to defend his title this week in the Cadillac Championship.

"Too early to tell," Woods said about playing this week at Doral. "I'll get treatment every day to try to calm it down. Just don't know yet. Wait until Thursday and see how it feels."

Woods has played a limited schedule this year - 10 complete rounds. He was to play twice more before the Masters on April 10-13.

Woods said the spasms were similar to what he felt last August at The Barclays, where he dropped to his knees after hitting one shot. Woods finished that tournament in a tie for second, one shot behind Adam Scott.

It was the second time in two years that Woods has walked off the course in the middle of the final round.

He quit after 11 holes at Doral when he was well out of contention - and then won Bay Hill two weeks later for his first PGA Tour title since his return from his personal chaos.

Guthrie said he could tell early on in the round that something was not right with Woods.

"He made a couple of uncharacteristic shots - the first on three kind of was the first one," Guthrie said.

"I didn't know if he wasn't feeling the greatest, and it kind of seemed like he might have been protecting - came up and out of it. I didn't think much of it until maybe 11. I noticed he was bending down gingerly.

"He didn't mention it to me," Guthrie said. "Obviously, he wasn't playing the greatest. I wasn't playing the greatest. He was battling out there. It's not like he was throwing in the towel. He was still trying."