Bubba Watson shot a final round of 63 to win the Travelers Championship by three strokes.
After falling off the pace in the third round, Rory McIlroy produced an encouraging display on the final day and carded a three-under 67 to finish on 11-under for the tournament.
However it wasn't enough to challenge Watson while Ireland's Seamus Power also shot a final round of 67 to leave him on six under overall.
The American Ryder Cup hopeful and two-time Masters Champion Watson carded eight birdies and only one bogey to finish clear of a group of four players including overnight leader Paul Casey.
The Englishman went into Sunday with a four-shot lead and an opening birdie strengthened his position further, but that was as good as it got as three bogeys saw him finish in a share of second with Americans Stewart Cink, JB Holmes and Beau Hossler.
Watson told Sky Sports Golf: "It was a fun round of golf and I got lucky that he (Casey) didn't have his best stuff today."
The left-hander's third win of 2018 confirms his impressive form ahead of next month's Open at Carnoustie and he also took the opportunity to send a message to his country's Ryder Cup captain.
"I'm looking forward to (the Open) and I'm hoping Jim Furyk's going to text and says, 'You're guaranteed for the Ryder Cup' - still waiting on that text!" he said.
"It's one of those years where you want it to keep going, you just don't want it to end."