Matthew Wolff carded a second successive eight-under-par 64 to move to the top of the leaderboard after the third round at the Rocket Mortgage Classic.
Wolff surged to a three-stroke lead through 54 holes thanks to another low round at Detroit Golf Club in Michigan on Saturday.
The 21-year-old is eyeing his second PGA Tour title after winning last year's 3M Open and the American is on track to add the Rocket Mortgage Classic trophy to his collection.
A shot off the pace at the start of day three, Wolff posted six birdies and two bogeys on the front nine to make the turn in 32.
After another bogey at the 10th, Wolff caught fire with two birdies and an eagle before another gain at the 17th moved him to 19 under overall – ahead of countrymen Ryan Armour (67) and Bryson DeChambeau (67).
Troy Merritt (67), Mark Hubbard (69), Seamus Power and Chris Kirk (70) are five strokes behind Wolff heading into the final round.
Kirk shared a one-shot lead with 2012 U.S. Open champion Webb Simpson following Friday's second round, but the former saw his advantage evaporate.
Simpson is one stroke further back in a tie for eighth after signing for a one-under-par 71 – his first round in the 70s this week.
Meanwhile, American star Rickie Fowler ended the day 10 strokes off the pace after shooting a third-round 69.