WASHINGTON (AFP) — South African Aldrich Potgieter sank a birdie putt from just inside 18 feet on the fifth playoff hole to win the Rocket Classic for his first US PGA Tour title.

The 20-year-old rookie grabbed the victory in just his 20th PGA start, beating American Max Greyserman in the hour-long playoff drama after American Chris Kirk had been eliminated on the second extra hole.

The playoff had returned to the par-three 15th at Detroit golf Club for the second time in the playoff when Potgieter, who had missed winning putts on the two prior extra holes, sank the winning putt after Greyserman missed a 34-foot birdie putt.

"Finally got one to the hole and saw the ball roll end over end and just knew it was going to go in," Potgieter said.

"I'm just happy to walk away as a winner."

Greyserman and Kirk each shot 67 and 54-hole leader Potgieter fired a 69 to finish deadlocked after 72 holes on 22-under 266.

Potgieter made two bogeys in the first five holes but battled back with birdies on three of the last six holes and a clutch five-foot par putt at 18 to make the playoff.

"It was definitely a tough day," Potgieter said.

"The start didn't go my way. I struggled to make putts, left a lot short."

All three birdied the first playoff hole, the par-four 18th, and at the first extra playing of the 15th, all three missed their birdie putts but Kirk missed his par effort from just inside four feet to drop out.

"Just really disappointed right now," six-time PGA winner Kirk said.

"I'm really happy with how I played. Just mis-read that last putt."

Potgieter and Greyserman both parred the par-four 16th and birdied the par-five 14th to set up the close, which made Potgieter the youngest South African to win on the PGA Tour.

"Big thanks to my family and friends, coaches and everyone who has been involved to get me to this point," Potgieter said, noting his family's sacrifice for his career.

"We had to give up a lot, moving to Australia, moving back. Emigrating is definitely not the easiest thing. Coming alone at the start of my career to the States and giving it a grind — having my dad here has helped so much."

Greyserman, twice a PGA runner-up last year, will have to wait longer for a breakthrough triumph.

"Unfortunately, I didn't get the job done," he said.

"I thought I hit a lot of good shots down the stretch. Very pleased with how I handled myself down the stretch.”

"Putts just didn't drop but I hit a lot of good putts. This one is going to sting for a little bit but I'll have to get back to work."

Potgieter's best prior PGA finish was a Mexico Open playoff loss to American Brian Campbell in February.

Americans Michael Thorbjornsen and Jake Knapp shared fourth on 267.