American Daniel Summerhays fired a nine-under-par 62 to grab a two-stroke lead over Canadian David Hearn heading into Sunday's final round of the John Deere Classic in Silvis, Illinois.
Defending champion Zach Johnson, the 2007 Masters winner and overnight co-leader, was lurking just off the pace another shot back at 16-under-par 197 after posting 67 at TPC Deere Run in the third round on Saturday.
Summerhays, looking for his first PGA Tour win, had 10 birdies against a lone bogey in ideal scoring conditions, using a string of three in a row from the 15th hole to vault to the top of the leaderboard.
Hearn, also seeking his maiden tour victory, posted eight birdies and one bogey in his 64, running off three successive birdies over the same stretch of holes from 15.
Tied for fourth on 198 were Americans J.J. Henry (65) and Jerry Kelly (66).
Australian Matt Jones and Americans Nicholas Thompson and Chris Kirk were another shot back. Two-time U.S. Junior Amateur champion Jordan Spieth, 19, was among three players on 200, six shots off the pace after three rounds.
(Reporting by Larry Fine in New York; Editing by Gene Cherry)