Rickie Fowler fired a 64 to open up a four-shot lead heading into the final round of the Waste Management Phoenix Open.
The American finished seven under for the day after amassing eight birdies to sit ahead of second-place Matt Kuchar.
Twice runner-up Fowler dropped just one shot on the par-three seventh, leaving him 20 under after 54 holes at TPC Scottsdale.
American Kuchar, chasing his third victory after wins at the Mayakoba Golf Classic and Sony Open in Hawaii, shot a blemish-free round of 65 to move ahead of compatriot Justin Thomas.
Thomas overcame an early stumble with two bogeys on the front nine to run off four birdies after the turn, signing for 68 and dropping into third place on 15 under overall.
Branden Grace and Byeong Hun An sit seven off the pace, tied in fourth at 13 under.
Meanwhile, Brandt Snedeker claimed the first birdie on the 16th, where the PGA Tour had placed Jarrod Lyle's golf bag and yellow hat on the tee in memory of the Australian who died from cancer aged 36 in August last year.
