Rory McIlroy fell five shots behind at the Genesis Invitational after a frustrating day on the greens at Torrey Pines.
The Northern Irishman shot a two-over-par 74 that included several missed putts, including one from under three feet at the 16th, leading to a double bogey.
A birdie at the par 5 18th hole after a nicely played bunker shot but a more positive outlook on the day, but the round left him five shots behind American Patrick Rodgers at the PGA Tour event.
Séamus Power also shot a 74 to lie tied 20th, while Lowry is tied 45th on four-over-par.
Rodgers carded a four-under 68 on Saturday to take a one-shot lead into the final round, as he picked up two shots on the front nine and three down the stretch before finishing with a bogey on the par-five 18th to head to the clubhouse on eight under.
Rodgers leads by one from compatriot Denny McCarthy, as he searches for his maiden PGA Tour victory.
Sweden’s Ludvig Aberg sits two shots back in outright third, thanks largely to an ace on the 140-yard par-three third.
England’s Tommy Fleetwood is among four players still in the hunt on four-under par, alongside Tony Finau, Patrick Cantlay and Davis Thompson.
World number one Scottie Scheffler shot a 76 to fall five shots back.