Swede Henrik Stenson picked up four shots in the final four holes to charge to a two-stroke lead after the third round at the Arnold Palmer Invitational in Florida at Bay Hill but it was a case of going backwards for Rory McIlroy.
World number three Stenson finished birdie, eagle, par, birdie to shoot six-under-par 66 in ideal conditions.
Stenson posted a 16-under 200 total, matching the best ever 54-hole score at Bay Hill, while American Morgan Hoffman (71) is alone in second place on 14-under.
Four players are three shots behind, including Australian Matt Jones, who birdied the final four holes, and defending champion Matt Every.
While Stenson surged, world number one Rory McIlroy backtracked with a 71 to fall seven shots off the pace after running up three consecutive bogeys from the 14th hole.
Speaking to Sky Sports, McIlroy reflected: "I'm frustrated. I birdied 12 and 13 and got right into the thick of things and then to give three shots back in quick succession was not really the plan.
"I'm disappointed with the way I finished but I played well for the most part. I need to try to get off to a good start tomorrow, shoot a good score and see where that leaves me.
"There's a lot of quality players above me. I would need to get off to a very fast start (to win). 30 or 31 on the front nine it's possible; just try to start better and go from there."
