Tiger Woods was dealing with a back injury as he finished 1-over par at Thursday's opening round of the Genesis Invitational.
Woods has never before won the tournament at the Riviera Country Club, which he has entered 12 times.
Woods told reporters after the first round that his back locked up on the 18th hole, which he said he "shanked."
"My back spasmed on it," Woods said. "It had been spasming over the last three holes and it just locked up on me and didn't move, didn't rotate."
Woods said he had previously suffered back spasms at home but had not recently experienced them during competition, according to ESPN's Mark Schlabach.