Cam Davis earned his first PGA Tour win, defeating Troy Merritt on the fifth play-off hole to clinch the Rocket Mortgage Classic trophy.

After going eagle-birdie on the final two holes of regulation to make the three-way playoff, 26-year-old Australian Davis triumphed over Merritt and Joaquin Niemann to reign supreme on Sunday.

It was the second consecutive week a marathon play-off was needed to determine a winner, after Harris English prevailed on the eighth extra hole to claim the Travelers Championship.

After the trio finished 72 holes at 18 under par, Chilean golfer Niemann went out on the first play-off hole, the par-four 18th, with a bogey his first of the week as he settled for his third runners-up performance this season.

Davis and Merritt duelled from there, matching scores on the 15th, 16th and 14th before returning to the par-three 15th hole again. 

There, Davis finally closed Merritt out, making par while the American bogeyed the hole. 

Davis became the seventh first-time winner on Tour this season. 

"It's been pretty hectic ever since the 17th hole for me, so I just tried to put as much out of my mind as I could and hit every shot for what it was worth," Davis told CBS after the round.

"As simple as that's said, it's so hard to do when the pressure's on like that, but I just kept on putting good swings on it. I didn't make any putts, but I kept on putting it in play, so it worked out all right."

Alex Noren (64) and Hank Lebioda (68) finished 17 under, while Bubba Watson (64) and Brandon Hagy (68) finished two back of the leaders at 16 under. 

Former world number one Jason Day had his best round of the week with a 66 but finished five strokes adrift of the play-off group, along with Keegan Bradley (68) and others. 

Among other notables, Patrick Reed (67) and Rickie Fowler (71) finished 10 under, while Phil Mickelson's third consecutive 72 left him at three under for the tournament.