Davis Thompson in pole position for second PGA Tour title at John Deere Classic

Defending champion Thompson signed for four under 67 around TPC Deere Run on Saturday, enough to move him to 15 under for the tournament, one stroke ahead of a chasing pack featuring fellow Americans Max Homa, David Lipsky, Bryan Campbell and Argentine Emiliano Grillo.

The American made the turn at even par but rallied on the back nine to roll in four birdies. It could have been even better, as he missed an eight-foot eagle attempt on the par five 17th hole. Thompson's ten-foot birdie putt on the 18th hole broke him free of a logjam that at one point featured no less than players tied for the lead.

"Nice to have some momentum going into tomorrow," the 26-year-old told AP.

Lurking one shot behind is Homa, whose had a difficult time of it of late. The former world number five has been in poor form while changing coaches, equipment and twice changing caddies.

"Golf has just been very boring for me this year," quipped the world number 99.

"I haven't had a whole lot of stress, and you want to be stressed out. So I look forward to the butterflies in the morning; I look forward to the first tee shot. It's just nice to get to feel that again. It's been a while."

36-hole leader Doug Ghim played his last 10 holes with two bogeys and no birdies and shot 74, pushing him outside the top 20.