JT Poston has followed his opening-round 62 with a six-under-par 65 to establish a healthy lead after two rounds of the John Deere Classic at TPC Deere Run.

Poston racked up four early birdies at the second through fifth holes on his way to reaching 15-under 127 at the midway stage of the tournament.

He leads Denny McCarthy by four strokes after McCarthy shot his own 65 to move to 11 under.

PGA Tour rookie Christopher Gotterup (67), Monday qualifier Chris Naegel (66), Austria's Matthias Schwab (65) and Argentina's Emiliano Grillo (64) are tied for third at 10 under.

Poston's approach game and putting were equally dialled in on Friday.

Three of his birdie putts were inside three feet, and another was just under five feet. But he also knocked in a 42 1/2-footer, uphill and left to right, for birdie at the par-4 ninth.

Poston tied for second at last week's Travelers Championship, but he is still in search of his first win on Tour since August 2019.

"Any time you're in contention, whether you've been leading since Thursday or the back nine on Sunday for the first time, any time you get up, there are some nerves," he said.

"There is some pressure. So thankfully I've put myself in that position a few times in my career and I know that I can do it."

McCarthy rolled in six birdies without a bogey to take sole possession of second.

The 29-year-old has never won on the PGA Tour.

Gotterup is making his fourth start since turning pro. He nabbed the Fred Haskins and Jack Nicklaus awards as college golf's player of the year while playing for Oklahoma, then made two of three cuts in his first three starts, including a tie for 43rd at the US Open.

After opening with a career-low 65 on Thursday, Gotterup posted a Friday card that featured four birdies, two bogeys and an eagle two at the par-4 14th. He reached the green with a 351-yard drive and made a 41-foot putt for eagle.

"Obviously we still got a long way to go here, but I do think that ... coming out of college I did think my game would translate really well to pro golf," Gotterup said.

"You look at guys that hit it pretty far, and I really improved my wedge game over the last couple years, so if I'm hitting the fairway, I got a lot of wedges coming into the greens.

"So I'm comfortable, and if I'm hitting it good, I don't see why I shouldn't play well."

Eight players are tied for seventh at nine under, including Maverick McNealy and Kelly Kraft, who shot 63s for the low rounds of the day.

Defending champion Lucas Glover rebounded from a first-round 74 with a 66 to get to two under, but he missed the cut by one.

Cam Davis is tied 24th after posting another three-under 68. He is at six under, with Aaron Baddeley (69,70) at three under.

They are the only two Australians to make the three-under cut.