Illinois - Defending champion Zach Johnson had five birdies in a five-under 66 to maintain a share of the lead alongside Lucas Glover and Patrick Reed on Friday at the USPGA John Deere Classic.
Reed, a USPGA Tour rookie, had an eagle and seven birdies and just one bogey in an eight-under 63, while former US Open champion Glover had nine birdies in a nine-under 62.
They topped the leaderboard on 12-under 130, one stroke in front of Australian Matt Jones who carded a 65 for 131.
Jerry Kelly and Troy Matteson both shot 64 to jump to 10-under 132. They were joined in fifth place by Canadian David Hearn (66), Kevin Streelman (66) and Daniel Summerhays (67).
Colombian Camilo Villegas, who shared the overnight lead with Johnson, struggled to a 73 to fall into a tie for 36th.
Glover, the 2009 US Open champion, launched his round by rolling in a seven-foot birdie putt at the 10th hole. He tapped in for birdie at 12.
Back-to-back birdies at 16 and 17 put him at seven-under for the tournament, and he made five more birdies coming in.
"I've been struggling. I was ecstatic to shoot three-under yesterday(Thursday)," said Glover, who hadn't broken par in back-to-back rounds since May.
"You can imagine how I feel today(Friday)."
Johnson got up and down for birdie at the par-five second and holed a birdie putt from off the green at the eighth.
The 2007 Masters champion drained a 13-footer for birdie at 12 and an 18-footer at 14 for another birdie. He regained a share of the lead when he got up and down for birdie at the par-five 17th.
"Today was a hard 66. Yesterday was a much easier 64," Johnson admitted. "I didn't drive it very well, but the positive side is I know I can play here if I don't drive it. My short game was tremendous. I putted great, and I chipped it even better."
Reed was in the first group out off the 10th tee on Friday and had birdies at 11 and 13 before a bogey at 14.
The 22-year-old rebounded with a 16-foot birdie putt at the 16th, then chipped in for eagle at 17.
After seizing the clubhouse lead, he praised his wife and caddie, Justine.
"She helps me with everything," he said. "I never check the wind. She tells me what the wind is.
"She helps me pick most of my clubs. She seems to know my distances better than I do. She's great at reading putts. So I kind of have the full package."
Leading second-round scores on Friday in the $4.6 million US PGA Tour John Deere Classic (USA unless noted, a-denotes amateur, par-71):
130 - Patrick Reed 67-63, Zach Johnson 64-66, Lucas Glover 68-62
131 - Matt Jones (AUS) 66-65
132 - Troy Matteson 68-64, Kevin Streelman 66-66, Jerry Kelly 68-64, David Hearn (CAN) 66-66, Daniel Summerhays 65-67
133 - Chris Kirk 67-66, Chez Reavie 72-61, Brendon de Jonge (ZIM) 65-68, Steve Stricker 67-66, J.J. Henry 68-65
134 - Martin Flores 67-67, Charles Howell 68-66, Jim Herman 66-68, Steve LeBrun 67-67
135 - Kevin Sutherland 70-65, Tom Gillis 67-68, Nicholas Thompson 69-66, Boo Weekley 66-69, Scott Langley 68-67, Jordan Spieth 70-65, Lee Williams 67-68
136 - Ken Duke 69-67, Bryce Molder 70-66, Joey Snyder 72-64, Chad Campbell 69-67, Y.E. Yang (KOR) 70-66, Roberto Castro 68-68, Brandt Jobe 69-67, David Mathis 70-66, Joe Affrunti 69-67, a-Patrick Rodgers 67-69