Stephan Jaeger also had a 66, while Adam Schenk joined them with the low score in the afternoon on the Copperhead course.

Jordan Spieth, back at Innisbrook for the first time in five years, had a bogey-free round and was particularly sharp with the putter, making some monster birdie putts on his way to a 4-under 67. Also at 4-under was former US Open champion Lucas Glover and Maverick McNealy.

This is the first time Brehm has made his way to the top of a leaderboard since he won the Puerto Rico Open last year in his final start to try to and save his PGA Tour card.

It hasn't been the smoothest road since then. Brehm has only made two cuts this season - and contested the no cut event at Kapalua - and is coming off an 80 in the second-round last week at The Players Championship.

"We've been grinding for a little while since then to try and find some good form again, and hopefully ... it's been showing signs of good play," Brehm said.

Jaeger had seven birdies in the morning, which started with temperatures cold enough for some players to wear beanies and extra layers.

Schenk finished his round with a 10-foot par save on the par-3 8th hole, and then after going bunker-to-bunker on the 9th, made a par putt from five feet.

Tommy Fleetwood carded a solid three-under-par 68, while the group at 69 included two-time defending champion Sam Burns and Justin Thomas, at No.10 the highest-ranked player in the field.

There are only two Australians in the field this week – Cameron Percy and Harrison Endycott.

They both shot one-over-par 72 to be tied 58th.