Playing the back nine first at TPC River Highlands on Thursday, Hughes was in blistering form as he strung together a run of five straight birdies from the 14th on his outward nine and picked up four more after the turn.

He had a long look at a magical 59 but left a 41-foot birdie putt short at his last.

"I've shot 61 twice in competition, once at Sea Island and once at a mini-Tour event," the 29-year-old said.

"Both times there was an outside chance the last few holes to shoot 59.

"Kind of similar deal to today where I kind of needed to birdie the last few holes."

LEADERBOARD

Also a back nine starter, McIlroy got off to a flying start by rolling in an 11-foot putt for an eagle on the par-5 13th and then followed up with birdies at 14 and 15 to quickly get to four-under.

The Northern Irishman's only miscue was a bogey at 16 but he was error free the rest of the way, piling on four more birdies after the turn for a seven-under 63.

"It's just been nice to get back into some competitive golf again," McIlroy said.

"You know, it doesn't feel the same because you're not having thousands of people reacting to your birdies and getting that going. I felt the weekends have been a little flat for me just because that's when you're in contention and that's where you sort of start to feel it. Thursdays and Fridays don't feel that different to be honest, but into the weekends they do."

American Xander Schauffele and Norway's Viktor Hovland, who were part of the afternoon wave, finished tied with McIlroy.

Lurking one shot further back is a pack led by Spain's Sergio Garcia and Phil Mickelson, who recently celebrated his 50th birthday, with both enjoying error free starts.

Joining the two major winners at six-under are Americans Tyler Duncan and Michael Thompson plus South Korea's Noh Seung-yul and South African Louis Oosthuizen.

Australians Cameron Davis and Mark Leishman were four-under, while Jason Day and Cameron Percy were a shot back.

Compatriots Greg Chalmers, Aaron Baddely and Cameron Smith were all one-under, while Matt Jones was four-over.

Golfers appeared to be taking heed and paying closer attention to COVID-19 safety protocols after PGA Tour Commissioner Jay Monahan issued a stern warning on Wednesday following the withdrawal of several players.

Major champions Brooks Koepka and Graeme McDowell pulled out of the event after their caddies tested positive for COVID-19 while Cameron Champ withdrew on Tuesday after testing positive.