Jason Dufner closed in on an historic PGA Tour double as he moved two shots clear at the Crowne Plaza Invitational at Colonial in Texas.
Dufner was 16 under par through eight holes of his final round at Colonial having increased his advantage over fellow American Zach Johnson.
The 35-year-old dropped a shot on the par-four second but bounced back nicely with birdies on five and six.
A victory for Dufner would make him the first player in PGA Tour history to win both North Texas events in successive weeks after his triumph at the Byron Nelson Championship.
Johnson is realistically the only man who can stop him - Tommy Gainey, Jim Furyk and John Huh are in a tie for third at seven under.
He is level par for his round, also through eight, after a birdie at three - which briefly saw him edge ahead of Dufner - was offset by a bogey at eight.
American Chris Kirk is the clubhouse leader following a wonderful 65 which gave him a four-round total of 275 - five under par.
