Troy Merritt fired a tournament-record 10-under 61 to join Kevin Chappell at the top of the leaderboard heading into the final round at the Quicken Loans National.
Merritt produced 11 birdies and a lone bogey to hurtle up the leaderboard and join Chappell, who carded a 67, on 14-under, with both men searching for their first PGA Tour title.
Rickie Fowler is one back on 13-under, ahead of a group of four players sitting on 12-under.
There was disappointment for former world number one Tiger Woods, as his dropped out of contention with a third-round 74 that leaves him on five-under, nine shots off the pace.
After opening rounds of 70 and 68, Merritt was one of the early starters at the Robert Trent Jones Golf Club on Saturday, and he would post a mark that was not matched until Chappell's 67 late in the day.
The 29-year-old Merritt birdied his opening five holes before a further birdie at the seventh was followed by a bogey at the eighth. Having taken the turn in 31, Merritt was far from finished, adding another five birdies in six holes from the 12th to the 17th to card a 61, the lowest round in the tournament's history.
Having begun the day on 10-under, the going was considerably slower for Chappell over the opening nine holes, with the 29-year-old picking up strokes at the second and the seventh.
Birdies at the 10th and the 14th followed, before the American dropped his lone shot of the round at the 16th. He would get that shot right back though, birding the par-four 17th for a round of 67.
After an impressive second-round 65, Fowler produced more of a mixed bag on Saturday, carding six birdies and three bogeys in a round of 68 to sit one shot off the pace.
Charles Howell III (67), Jason Bohn (67), David Lingmerth (68), and Kim Meen-whee (67) are a further shot back on 12-under. Second-round leader Ryo Ishikawa, shot a 71 to end the day in a tie for eighth at 11-under alongside defending champion Justin Rose (65), Carl Pettersson (64) and Bill Haas (64).
There was disappointment for Woods as the 14-time major winner slumped to a three-over-par 74 on Saturday, undoing the good work done through opening rounds of 68 and 66.
Woods produced the erratic form off the tee that has seen him struggle in recent months, with the 39-year-old missing his first six fairways and hitting just 10 of 18 greens in regulation on a day in which he produced two birdies, three bogeys and a double bogey at the par-three 11th.