Brooks Koepka cruised to victory Sunday in the World Golf Championships-FedEx St. Jude Invitational at TPC Southwind in Memphis, Tennessee.

Koepka carded a five-under 65 in the final round to finish at 16 under for the tournament, three shots better than Webb Simpson. 

This is his third victory of the PGA Tour season and the seventh of his career.

FedEx St. Jude Invitational Leaderboard

1. Brooks Koepka (-16)

2. Webb Simpson (-13)

3. Marc Leishman (-12)

T4. Tommy Fleetwood (-11)

T4. Matthew Fitzpatrick (-11)

T4. Rory McIlroy (-11)

7. Jon Rahm (-10)

8. Ian Poulter (-9)

T9. Bubba Watson (-8)

T9. Billy Horschel (-8)

Down the stretch, Koepka was basically golfing against himself.

Simpson moved up the leaderboard after shooting seven under Sunday, but he teed off an hour before Koepka. By the time the four-time major champion was wrapping up the back nine, Simpson had long been confined to the clubhouse.

Rory McIlroy, who led Koepka by one stroke through 54 holes, was never much of a factor toward the end, either. McIlroy made the turn at even par, ceding ground to Koepka in the process. A bogey on No. 12 was effectively the final nail in the coffin, and he wound up in a tie for fourth at 11 under.

Even the enthusiasm from his birdie on No. 14 was short-lived, as he bogeyed the 15th hole to slip back to 11 under.

Koepka, meanwhile, was rolling. His work with the putter was particularly impressive. He went bogey-free in the final round despite reaching just 11 of the 18 greens in regulation, per PGATour.com. His 1.545 putts per GIR and 3.652 putting strokes gained were his best single-round scores of the tournament.

As if any doubt about the outcome remained, Koepka removed the remaining drama on No. 17. His second-shot approach landed in the middle of the green, and he sank a tricky birdie putt:

The Associated Press' Doug Ferguson and Action Network's Jason Sobel added some perspective to the result:

Koepka is a two-time winner of the PGA Championship and U.S. Open. Although the St. Jude Invitational isn't the most prestigious stop on the PGA Tour calendar, coming out on top meant a lot for the 29-year-old:

Koepka is first in the FedExCup standings and World Golf Ranking. The fact he has more major wins (four) than non-major wins (three) remains confounding, but there's no question he's the best golfer in the world right now when he's dialed in.

Elsewhere in the tournament, Jon Rahm finished seventh at 10 under, two places better than Bubba Watson. Jordan Spieth, Patrick Reed and Justin Thomas tied for 12th at six under. Dustin Johnson earned a share of 20th place after going five under. U.S. Open champion Gary Woodland capped off a poor tournament by going two over Sunday to end in a tie for 55th.

The Wyndham Championship at Sedgefield Country Club in Greensboro, North Carolina, is the next stop on the PGA Tour. The event tees off Thursday.