American Patrick Cantlay leads the Genesis Invitational by two shots heading into the final round.
Cantlay, 31, had a five-shot lead at the halfway point, but his advantage was reduced after he struggled to reach a score of under 70 in his third round on Saturday.
Xander Schauffele and Will Zalatoris both carded 65s to move to 12 under overall – two behind Cantlay.
World number two Rory McIlroy made five birdies and three bogeys as he carded a 69 and is 27th at four under.
The four-time major champion is joined by Englishman Tommy Fleetwood, who shot a 71 at Riviera Country Club in California.
Cantlay, seventh in the world rankings, opened with a birdie, but gave it back at third when he missed a seven-foot putt to save par.
He then recovered to make birdies at the 11th and 13th to climb to 15 under, before problems teeing off the penultimate hole led to a bogey.
Fellow American Schauffele, meanwhile, got off to a strong start with an eagle at the par-five opener and made four birdies in his final nine holes, while fellow American Zalatoris made seven birdies and just one bogey.