Adam Hadwin (-6) fired an opening-round 66 at the Memorial at Muirfield Village on Thursday, though a host of PGA Tour stars — Scottie Scheffler (-5), Collin Morikawa (-4), Xander Schauffele (-4), Ludvig Aberg (-4) — are hot on his tail.

Hadwin, coming off a missed cut at his native RBC Canadian Open last week, recorded eight birdies and two bogeys, carding 33s on the front and back nine. Hadwin, ranked no. 59 in the Official World Golf Ranking, has one career PGA Tour victory, at the 2017 Valspar Championship.

“It's only Thursday, a lot of golf left,” Hadwin said after. “I played a really solid round of golf today. I was in play off the tee, I hit a bunch of greens, I had some good looks, and then kind of it got going on the back nine. I hit a few wedges close…It's just one round. I've always said you can never win the tournament, but you can lose it, and so I haven't lost the tournament yet.”

Last year, Hadwin opened with a sturdy 69 at Jack's Place, only to tumble out of contention with a second-round 79.

“At the time, mentally, I probably wasn’t prepared to handle that and fight through to the finish, and I think right now, I feel like my game has been getting better,” Hadwin said Thursday. “The results haven’t shown it, but I’ve been trending where I want it to go, and I think today was just a bit of a culmination of that.”

Muirfield Village, due to its rare combination of length, thick rough, and small greens, has historically rated as one of the tougher venues in golf. Some rain over the past few days softened the conditions on Thursday.

World no. 1 Scottie Scheffler, making his first appearance since felony charges were dropped, made six birdies and one bogey.

“Going out this morning, a little softer greens, a little softer fairways, and was able to put up a good score,” said Scheffler. “It felt like I hit a lot of quality shots today, it felt like my ball striking was really good, and I was able to hole a few putts as well, so overall, pretty pleased with the round today.”

Morikawa, like Hadwin, ended his day with a disappointing bogey on the par-4 18th, but otherwise called his round “really good.” Morikawa has been in-form with his irons since the Masters, resulting in four top-four finishes (but no wins).

“Look this is a tough golf course and it's going to play tough,” said the two-time major champ. “Very unfortunate finish … from where I was at in the fairway or in the bunker I would have taken a par, but after I hit that shot, obviously I wish I had the putt. But overall still really, really solid.”

Xander Schauffele, in his first start as a major winner, made up for a “sloppy” day of driving with pristine work on the greens. The no. 2 player in the world hit eight of 14 fairways but led the field in putting en route to a bogey-free 68.

“I'm happy with how I played, with how I stuck in there and really happy my short game bailed me out on a day that could have been a lot worse,” he said.

Elsewhere on the leaderboard, Corey Conners rode an elite ball-striking day to a 4-under 68. Viktor Hovland (-3) built on the form he (finally) found at the PGA Championship.

Other notables: Rory McIlroy (-2), Justin Thomas (-1), Max Homa (-1), Hideki Matsuyama (+1), Jordan Spieth (+2). Auburn freshman — fresh off winning every NCAA award and the natty — Jackson Koivun began his PGA Tour career with an even-par 72.

As the penultimate Signature Event on the PGA Tour calendar, the Memorial awards $4 million of its $20 purse million to the victor. As one of three “legacy invitationals” (Tiger Woods' Genesis, the API), Jack Nicklaus' event features a smaller field and friendly cut. The top 50 of 69 — plus ties and anyone within 10 strokes of the lead — will advance to the weekend.

“I think that's exactly what we were trying to do as a Tour,” Schauffele said about the star-studded Day 1 leaderboard. It's the product we want to put out. When you look up at that board you want to see everyone's name as high up there as possible hashing it out on Sunday. That's what people want to see and that's what we want to give 'em.”

The U.S. Open at Pinehurst No. 2 begins next week.