James Hahn is in pole position to win a third PGA Tour title as he leads the AT&T Byron Nelson following a collapse by Jason Kokrak.
Hahn struck six birdies in his six-under-par 64 to sit at the top of the leaderboard on 12 under going into the final round.
Kokrak will be kicking himself after he blew a five-shot overnight lead. The American put himself in line for a first tour win with a career-best round of 62 on Friday but he went round in 10 more shots on day three, thanks in part to a triple-bogey six at the par-three fifth.
He is still in contention on Sunday, though, two shots behind Hahn and one behind second-placed Billy Horschel.
Jason Day struck the round of the day as his 63, consisting of eight birdies and a bogey, saw him surge up the leaderboard and join Kokrak on 10 under.
Defending champion Sergio Garcia will still harbour hopes of retaining his title after a 64 moved him up to eight under, but world number one Dustin Johnson looks out of contention after his one-over-par 71 saw him drift to seven shots off the lead.
Ireland's Seamus Power also fell back on day three, dropping to even par after a turbulent round of 72 that featured four birdies and six bogeys.
