Tiger Woods blames back spasm for horrendous shank at Genesis Invitational

Woods, 48, is still adapting to ankle fusion surgery, having undergone treatment in April last year after withdrawing from the Masters during the third round and he did not compete again until the Hero World Challenge in December.

The 15-time major champion finished Thursday's opening round at the Riviera Country Club on one-over par after shanking his second shot on the 18th from the fairway over into the trees on the right.

Woods eventually sunk a two-putt bogey to make a five, and afterwards revealed he would need some treatment to get himself back out on the course again on Friday.

"My back spasmed on it," Woods said in his post-round interview to the Golf Channel when asked about the shank on the 18th hole.

"It's been spasming the last three holes, and it just locked up on me. Didn't move, didn't rotate, and present hosel first."

Woods, who previously said he expects to participate in one event per month this year, added: "We have got some treatment ahead of us and some work to do, to be ready for tomorrow.

"But that's just part of the deal, and (I) look forward to the challenge."

Former world number one Woods hit eight fairways, 10 of 18 greens, and took 30 putts in the opening round.

"My round was good and a little bit indifferent," said Woods, who had opened with an up-and-down birdie on the par-five first.

"I struggled with the speed of the greens, even though I made a few.. and was stressing out on the short game, I had maybe like five pars today."

Patrick Cantlay was the early leader with his round of 64, one shot ahead of Australians Cameron Davis and Jason Day, alongside Luke List. Jordan Spieth was among the group two adrift at five-under.

READ MORE: Tiger Woods believes PGA Tour can go it alone without Saudi money