Justin Thomas holds the trophy after winning the World Golf Championship-FedEx St. Jude Invitational Sunday, in Memphis, Tenn. (AP Photo/Mark Humphrey)

MEMPHIS, Tenn. (AP) — Justin Thomas wants to make his second stint as No. 1 in the world last longer than the first time around.

“I hope so,” Thomas said Sunday after winning the FedEx St. Jude Invitational to take the No. 1 spot for the first time since June 2018. “I feel like I’m a better player, and I feel like I’m more complete of a golfer now than I was then.”

Thomas dueled defending champion Brooks Koepka down the final holes, sealing the World Golf Championship victory on the par-5 16th. Thomas took the lead for good with his second straight birdie, while Koepka bogeyed the hole.

Koepka pulled within a stroke with a 39-footer for birdie on No. 17. But Koepka put his tee shot into the water along the 18th fairway on his way to double bogey, allowing Thomas to finish up an easy par putt for what wound up a three-stroke victory.

Thomas closed with a 5-under 66 to finish at 13-under 267 and take the $1.8 million winner’s check from the $10.5 million purse for his 13th PGA Tour title. At 27, he became the third-youngest player since 1960 to reach 13 PGA Tour wins, trailing only Tiger Woods and Jack Nicklaus.

“I’ve been fortunate to have a good career so far, but I plan on playing out here for a long time and have a lot of things that I still want to accomplish,” Thomas said. “And every milestone and steppingstone is hopefully something that I can learn from and something that will help me even more in the long run.”

One sign of Thomas’ growth was this was the fifth time he rallied to win, and he matched his biggest comeback after starting the day four strokes back of third-round leader Brendon Todd. Thomas has three wins this season, two since the start of the year.

The last time Thomas was No. 1, he spent four weeks at the top of the ranking. He will supplant Jon Rahm, who became No. 1 after winning at Memorial two weeks ago and tied for 52nd this week.