The former World No.1 is three shots behind outright leader Matt Wallace at TPC Craig Ranch, while compatriot Min Woo Lee also shot a first-round 66 on Friday (AEST) to sit level with Day.

Harrison Endycott will begin his second round a further shot back from that pair, while Aaron Baddeley (68) and Adam Scott (69) completed a solid day for the Australian hopes.

Seven others were a shot back from Wallace before a rain-delayed round with preferred lies was suspended by darkness with nine players on the course.

Day was four-under at the turn before mixing two bogeys with three birdies on a testing back nine, his last on the par-5 9th.

“The one thing that let me down was the short game,” Day said post-round.

“It’s been nice to be able to improve the irons.

“I think overall the average winning score is 22-under around here.

“You kind of have to shoot five, six-under a day, somewhere in that region.

“Kind of on par right now, so good. Got three more days left.”

Day closed with a brilliant 62 at TPC Craig Ranch 12 months ago to finish 23-under-par, a shot ahead of Austin Eckroat and Si Woo Kim.

It was the Queenslander’s 13th career PGA Tour title, but his first since winning the Wells Fargo Championship in 2018.

“If you give yourself the correct opportunities off certain holes, you can get momentum rolling your way very quickly,” he said.

“It’s one of those courses where you can go around and look at the holes and go, ‘I’m going to birdie this, going to birdie this, going to birdie this, going to par this, going to birdie this’.

“So, if you can take those opportunities, and I feel like my game suits it pretty nice around this course, that’s kind of how I play this course.”

Wallace, who has missed the cut five times and doesn’t have a top-10 finish in 11 tournaments this year, birdied five of the first six holes and capped his bogey-free, career-low round with a tap-in birdie on the 18th.

– Murray Wenzel