Rory McIlroy will head into the final round at the BMW Championship four strokes off the lead after firing a round of 65 on Saturday night.
The Co Down man's round was flawless as he managed seven birdies to move to 17 under par.
It leaves him four strokes off Bryson DeChambeau, who continued his imperious Friday form into the opening nine but struggled after the turn, alongside Patrick Cantlay.
Meanwhile, Shane Lowry had a mixed day as a round of 71 saw him move to six under par. Things had started so well for the Offaly man as he birdied 2, 4 and 5.
He picked up further shots at 12 and 13, but bogeys on 9 and 15 and a double bogey on the par three 17th pushed him back to a tie for 40th.
American DeChambeau signed for a career-best of 60 in Baltimore in his second round and cantered to a strong lead with back-to-back eagles on the fourth and fifth on Saturday.
He reached the 10th on a six-under 30 but made hard work for himself after the turn, carding two bogeys and a double bogey across four holes to finish on 67 and 21 under for the tournament.
This was good enough to share the lead with Cantlay, who eagled the second and picked up five more shots before bogeying the 18th in a round of 66.
Sungjae Im is third on 18 under, a shot ahead of a quartet including McIlroy and Sam Burns who both carded a 65.
World number one and US Open winner Jon Rahm hit a 70 to sit eighth on 16 under, while Paul Casey is tied for 16th on 10 under and Lee Westwood is two shots behind that tied for 26th.