World number three Cameron Smith headlines a six-way tie atop the Memorial Tournament leaderboard after Thursday's first round at Muirfield Village.

Smith is joined by American trio Luke List, Cameron Young and Davis Riley, as well as Canada's Mackenzie Hughes and South Korea's Lee Kyoung-hoon.

It is the largest leading group after the first round in tournament history, but they all got to their five-under 67 in different ways. 

Young finished the day second in average driving distance (316.8 yards), behind only Jon Rahm, while Lee, Hughes and Smith finished top-six in putts-per-green-in-regulation.

List was the only member of the leading group to finish with less than two bogeys, and Riley played an all-round game; top-15 in driving distance while being dialled in with his putter down the back-nine, going five-under from the 11th hole to the 17th.

US PGA Championship runner-up Will Zalatoris is part of the three-man group one stroke off the lead, while Max Homa and Canada's Corey Conners are in the logjam at three under.

A star-studded group finished with a two-under 70, including Rory McIlroy, Jordan Spieth, Xander Schauffele and Im Sung-jae, while Chile's Joaquin Neimann is with Collin Morikawa and Jason Day at one under.

Patrick Cantlay and Rahm were even-par, Mito Pereira will need a solid second round to make the cut after a one-over finish, and Hideki Matsuyama was handed his first career disqualification for using a wood with paint on its face – deemed illegal. He was three over at the time of the incident.

World number one Scottie Scheffler was part of an eight-man group atop the leaderboard after the first round of the Charles Schwab Challenge, played at Colonial Country Club in Texas.

Scheffler, who shot a bogey-free 66 despite only hitting 50 per cent of the fairways in regulation, was joined by fellow Americans Harold Varner III, Chris Kirk, Beau Hossler, Patrick Reed and Webb Simpson, as well as Canadian Nick Taylor and Australian Cam Davis.

Hossler produced the most notable round, with two eagles – both coming on par-fours – in his last four holes to fly up the leaderboard.

One shot off the lead were a group including Davis Riley and Kevin Na, while pre-tournament favourite Jordan Spieth was back at one under, tied with Victor Hovland and Max Homa.

Spieth, who is from Texas, has an impeccable record at Colonial, with seven top-10 finishes – including three runners-up and a win – from nine starts on the PGA Tour.

Speaking to the media after finishing his round, Spieth said he is battling his putter at the moment but that he is confident things will turn in his favour.

"I think I'm typically more comfortable with reads here, although today here was totally different, I misread a number of putts today," he said.

"But I stroked it beautifully, I just felt great about the way I putted, I just didn't get much to go.

"Those are the kind of rounds where you can either look at it negatively, or you can say at it like 'hey, that lid is going to come off one of these times, and all of a sudden they're all going to pour in'.

"It's done that for me [previously] at Colonial, so I think that's the attitude I'm going to take."

At even par were a strong international group including Chile's US PGA Championship main character Mito Pereira, Colombia's Sebastian Munoz, England's Ian Poulter, American Collin Morikawa and the South Korean duo of Lee Kyoung-hoon and Im Sung-jae.

PGA Championship winner Justin Thomas was at one over, while his playoff opponent last week Will Zalatoris was a shot further back at two over.

Max Homa held on down the stretch to win the Wells Fargo Championship for a second time at TPC Potomac at Avenel Farm.

The 31-year-old finished eight under after a two-under 68 on Sunday, eventually winning by two strokes, but it was anything but smooth sailing.

Starting the day at six under, Homa birdied the opening hole as well as the fifth, and after a bogey at seven, he responded strongly with back-to-back birdies on nine and 10.

The 2019 champion was locked in a tight battle with 54-hole leader Keegan Bradley, who double-bogeyed the second hole and the 11th. Another Bradley bogey at 15 allowed Homa to open up a three-stroke lead with a birdie on the same hole.

But the margin was cut back to one just a hole later as the roles reversed on the 16th, where Homa had to sink a tricky bogey putt to avoid the scores being levelled.

After both made par on the difficult par-three 17th, Homa teed off on the last with a one stroke lead, and he had the luxury of seeing Bradley put his drive in the bunker first to take the pressure off. Homa made no mistakes, taking even par to seal the two-stroke win as Bradley bogeyed.

It is the American's fourth career PGA Tour win and second of the season after winning the Fortinet Championship in September to kick off the 2021-22 calendar.

Speaking to the media after stepping off the 18th green, Homa said he and his caddy had been reminiscing about how much had changed since their first career win at this tournament at the Quail Hollow Club and paid respect to Bradley for a gripping battle.

"It's crazy, I was thinking about it when I was walking to the first tee," he said.

"[Caddy] Joe [Greiner] and I were talking about it in 2019 – I was leaning on Joe to help me, he was talking about getting to the tee after Rory [McIlroy] so I didn't have to hear the roar. 

"I didn't have to deal with that [this time] – I've got a great support system on this tour. [The crowd was] a little crazy, but it's super awesome. I'm coming into my own, I'm starting to believe in myself a lot, and that's all I can ask for.

"Keegan is a really good golfer – he hits it so well, and he holed some really good putts. 

"I was just trying to play my game and see what happened – he made an unbelievable birdie on 16 while I was trying not to make double. 

"I knew he was never going to go away – I was watching the guys behind – but I felt like eight or nine under was going to be pretty good, and I was just focusing on hitting good shots and not worrying about the bogeys."

In a tie for second at six under were Matt Fitzpatrick and Cameron Young, with the latter's final-round 66 matching the second-best score of the day.

After finishing round two right on the cut-line, Rory McIlroy produced two consecutive 68s to claim outright fifth place at four under..

The round of the day belonged to Stewart Cink, with his five-under 65 seeing him shoot up into the top 10.

Jason Day will head into the weekend at the Wells Fargo Championship as a strong favourite after extending his first-round lead to three strokes in Friday's action.

After posting a 63 in much friendlier Thursday conditions, Day was solid again, birdieing two of his first three holes, and was four under through 13. 

After a bogey on 14 and 17, he ended his day on the right foot with a birdie on 18 for a three-under 67, sitting at 10 under through two rounds.

Day, who has not won a PGA Tour event since 2018, told the media after stepping off the 18th green that he is excited to be back in this position after previously spending 51 weeks as the world number one before a number of injuries.

"I'm looking forward to it – it's nice to be back in the mix, nice to be leading," he said. "It's still two more days left, so I can't get too far ahead of myself.

"I mean, not many times you see this hair (after being forced to play without a hat due to the rain), but hopefully this weather can kind of go away and we can have hats on for the weekend.

"When you have conditions like this, it's really hard to commit to a shot because you're going in there and you're doing it kind of a lot quicker than your normal pre-shot routine.

"You have to force yourself to hit the shot and trust that."

Max Homa has a hold of outright second at seven under after posting a 66 – tied for the second-best round of the day. Also shooting 66 was Luke List, who drove the green on the par-four 14th hole to putt in for eagle, flying up the leaderboard into a tie for third at six under.

One shot further back at five under is a small group highlighted by Keegan Bradley, who had the round of the day with seven birdies and two bogeys for his 65.

A strong international contingent is in a tie for 10th at four under, with English duo Tyrrell Hatton and Matt Fitzpatrick, as well as India's Anirban Lahiri and Slovakia's Rory Sabbatini.

Abraham Ancer is part of the group at three under, while some big names are a further shot back, including Tony Finau, Sergio Garcia, Rickie Fowler and Camilo Villegas.

Rory McIlroy, Corey Conners and Matt Kuchar will live to see the weekend after finishing right on the cut line at even par, while Aaron Rai was not so lucky, going from a bogey-free 65 on Thursday to a birdie-free 76, missing the cut at one over.

Also missing the cut was Charl Schwartzel, Francesco Molinari, Marc Leishman and Webb Simpson.