-21 Z Johnson (US) -18 B Davis (Eng) -17 J Overton (US), B Crane (US) -16 S Verplank (US), B Molder Selected others: -13 M Laird (Sco) -12 P Casey (Eng), KJ Choi (Kor) -9 V Singh (Fiji) -3 J Daly (US) level J Rose (Eng) +7 I Poulter (Eng)
Johnson's last win on the US Tour came at the Valero Texas Open in May, 2009
A record-breaking display from American Zach Johnson denied England's Brian Davis victory at the Crowne Plaza Invitational at Colonial on Sunday.
Davis led by a shot at halfway in the final round but was one over par on the back nine to finish 18 under, Johnson's 64 giving him a three-stroke win.
Johnson's total of 21 under is a record score for the Texas tournament.
American duo Jeff Overton and Ben Crane tied for third on 17 under with Paul Casey joint 15th on 12 under.
Casey's four-under, bogey-free 66 in the final round was his third such score of the tournament, with only Friday's par-round of 70 denying him the opportunity to challenge on Sunday.
If I keep knocking on the door, I am going to get one soon
Scotland's Martin Laird completed a solid week with an eagle on the par-five first on his way to a 65 and a 13-under total.
Justin Rose finished with a 70 to end the tournament on level par, while Ian Poulter endured a nightmare final-round 76 to finish last on seven over.
Fellow Englishman Davis' final-round 68 was his worst of the event, leaving him as runner-up on the PGA Tour for the second time in six weeks.
He lost a play-off to Jim Furyk for the Heritage Classic at Hilton Head on 18 April after calling a two-stroke penalty on himself at the first extra hole, but the 35-year-old remains confident that his persistence will pay off.
"If I keep knocking on the door, I am going to get one soon," said Davis, who had missed three successive cuts coming into this event.
"It's been a great week. If you would have said at the start of this week, after three missed cuts in a row, you are going to finish second, you would be delighted."
"I had a chance today, I just couldn't get over the hump. Zach played great. He won the tournament, I didn't lose it."
"Overall, though, I played great, I didn't have many bogeys this week. I just came off three missed cuts. There are a lot of positives to take from it."
Davis' downfall came during the second half of his round where he was unable to match the three shots he gained on the front nine and finished with a bogey on the 18th.
In contrast, Johnson produced a superb back nine, picking up five birdies, with only one dropped shot on the 14th, on his way to a second successive 64.
Johnson was one of 10 Americans in the top 12, including Ryder Cup captain Corey Pavin (15 under) and 2008 Ryder Cup player Boo Weekley (14 under).