A day after winning the PGA Tour's Memorial, he went 36 holes as a caddie in U.S. Open qualifying.

Hovland, who won in a playoff on Sunday at Ohio's Muirfield Village – earning $US3.6 million ($A5.4m) for his troubles – was on the bag for Zach Bauchou, his former roommate at Oklahoma State.

This was not planned all that far in advance.

"We went to dinner on Saturday and I jokingly said, 'Why don't you come caddie on Monday?'," Bauchou said.

"He said, 'Dude, I will'. If he says he's going to do something, he'll do it."

Hovland was one shot off the lead after 54 holes at the Memorial. He closed with a two-under 70 and then won with a par in the play-off over Denny McCarthy.

Bauchou failed to qualify, posting a 72 at The Lakes Golf & Country Club and making only one birdie in his round of 76 at Brookside.

"He said, 'Dude, I will'. If he says he's going to do something, he'll do it." – Zach Bauchou.

The pair were teammates in 2018 when Oklahoma State won the NCAA title with a team that also included Matthew Wolff and Austin Eckroat.

Hovland, a 25-year-old from Norway, still lives in Stillwater, Oklahoma.

Without the Memorial champion living up to his word, Bauchou said he would have carried his own bag.

"It was nice to have him come out and caddie," Bauchou said.

"He's been a good friend for a long time. He's a good person."