Scott fired a solid opening round at TPC Harding Park in San Francisco with a 68 leaving him in contention at two-under-par, just three shots behind clubhouse co-leader and fellow Australian Jason Day.

Day's 65 was later matched by American Brendon Todd.

It was Scott's first competitive round since March and there were fears Scott might be rusty for the first major of 2020.

The former world No.1 mixed three birdies with three bogeys on the front side before picking up two shots coming home.

"I'm very happy with my round. It wasn't really rusty, only a little bit," Scott said.

"If I can just correct that for tomorrow and get three or four more tee shots in the fairway, I can create some opportunities."

Scott witnessed a bizarre incident on Thursday when DeChambeau's unprecedented swing speed caused the shaft in his driver to snap shortly after his tee shot at the seventh hole.

DeChambeau, who has added 10kg of muscle to his frame and significantly increased his driving distance in the past year, was allowed by a rules official to have a team member in the gallery fetch a new shaft from his car to replace it.

That was because the damage was caused in the process of hitting a shot.

Scott is one of the US PGA Tour's longer hitters but joked the media hype around DeChambeau's power was underwhelming in person.

"He's hitting it long; there's no doubt about it," Scott said after his round.

"Not to, like, put him down but I thought it was going to be longer (laughter). There's been so much build-up, me reading the news and listening to him and watching him play, I thought I was going to see like one of those long-drive guys.

"Fortunately, I still hit it long enough."

Scott is chasing a second career major title to go with his 2013 Masters triumph.

Recent form suggests that win could come at the PGA Championship, where he has finished third and eighth in the past two editions.

The US PGA Championship is renowned as the major that most favours big bombers, such as two-time defending champion Brooks Koepka.

But 40-year-old Scott knows he can still match it with the heavy hitters and combine it with his superb iron play.

"The (PGA Championship) courses have suited me the last couple years," Scott said. "They are difficult, but if you drive it well and you're solid with your irons and you can (contend)."

Australian Associated Press