Former U.S. Open champion Webb Simpson, Michael Thompson, Cameron Champ, Lee Hodges and Matt Wallace are two shots back.

Cam Davis is the leading Australian, an opening 68 leaving the defending champion four shots off the pace at Detroit Golf Club.

Finau, who rallied from a five-shot deficit with 11 holes left to win the 3M Open by three shots Sunday in Minnesota, had five birdies on his front nine.

After cooling off with four straight pars, Finau closed with his seventh and eighth birdies in a bogey-free round. He hit all 18 greens in regulation for the first time in 728 PGA Tour stroke-play rounds.

"Do the math, I missed 10 putts," he said. "Obviously, 64's a very good round, but this is a golf course where a lot of guys are going to make birdies."

Pendrith, a 31-year-old PGA Tour rookie, surged into a share of the lead with five birdies in a seven-hole stretch on his back nine.

RIGHT: Defending champion Cam Davis is the best of the Aussies after round one in Detroit. PHOTO: Mike Mulholland/Getty Images.

Toward the end of his round, the relatively anonymous player in the world noticed the 'h' in his last name was missing on the leaderboard.

Alas, the eight-under next to his misspelled name was correct.

"That's all that matters," he said with a grin.

Pendrith is atop a leaderboard for the first time on the PGA Tour following an opening round. The Canadian did have the third-round lead by three shots last October at the Bermuda Championship before closing with a 76 and finishing a career-high fifth.

In March, he was 13th at the Players Championship and came away with a career-best $US327,222 ($A468,000) – and a broken rib.

The injury prevented him from competing for nearly four months, leading to him being ranked No.237. He has bounced back with ties for 11th and 13th at tournaments earlier this month.

"When I'm healthy, I can compete with the best," Pendrith said.

Davis is tied for 22nd, one stroke ahead of Australia's former World No.1s Jason Day and Adam Scott, who both posted three-under 69s.

Aaron Baddeley is a further shot back, with Cameron Percy (73), Geoff Ogilvy (74) both over par and Brett Drewitt almost certain to miss the cut after an opening 80.

The field includes five players in the world's top-20, doubling last week's total in Minnesota, and Finau was the only one of them to fare well in the first round.

Defending FedExCup champion Patrick Cantlay, the World No.4, and 13th-ranked Will Zalatoris both carded 70s. Cameron Young, ranked 19th, was another shot back and 20th-ranked Max Homa had a 72.