Rory McIlroy sits in second spot heading into the final round at the Genesis Invitational at Riviera Country Club but he trails the inspired leader Jacob Bridgeman by six strokes.
Starting third overnight, McIlroy carded a two-under par 69 on Saturday to climb to second place, as Friday's joint-leader Marco Penge struggled to a three-over 74.
But the other leader at the midway point, Bridgeman, stamped his authority on the tournament and sped clear of the field, with a stunning seven-under par 64.
It was early on the back nine when Bridgeman really copper-fastened his lead, with three birdies and an eagle between 10 and 14. The 26-year-old American even missed a short birdie putt at the end to miss a chance to get to 20-under after 54 holes.
Playing in the group ahead, McIlroy had an often frustating afternoon, missing several birdie opportunities on the back nine, including a three-putt on the par-5 17th.
Birdies on the par-5s at the first and 11th holes and the short sixth, as well a dropped stroke at the 10th saw him post a two-under par round.
McIlroy is one stroke ahead of South Africa's Aldrich Potgeiter in third, with England's Aaron Rai a shot further back on 11-under.
Xander Schauffele and Kurt Kitayama sit in tied-fifth on 10 under.
Earlier, Shane Lowry had likewise carded a 69 to sit in tied-32nd on three-under par overall. Lowry was on course for a strong round, with four birdies in a blemish-free opening 15 holes, until two dropped strokes in the final three holes.
