Nick Watney joined Phil Mickelson in a share of first place at the end of three rounds at the Wells Fargo Championship in North Carolina but birthday boy Rory McIlroy fell three shots off the lead.
On a windy day at Quail Hollow, Mickelson could only manage a one-over round of 73, carding three bogeys and a double-bogey at the 15th to open the door for Watney who signed for a 71 despite a double-bogey of his own at the 17th.
They sit together at the top on eight under par for the tournament, with George McNeill one shot further back in second after a par round of 72.
McIlroy, who turned 24 on Saturday, started the day in a share of fifth but, despite an eagle on the par-five seventh, never really found his rhythm and double-bogeyed the ninth to sign for a one-over 73.
That dropped him down to a five-share way of 10th place. The world number two, who won here in 2010 and was only beaten in a play-off last year, cannot overhaul Tiger Woods at the top of the rankings this weekend, but was hoping for a victory to close the gap.
The big movers on the day were John Senden and Ryan Moore.
Senden had the round of the day with a five-under 67, spoilt only slightly by a bogey on the 16th, that catapulted him from a share of 35th to join Moore, Robert Karlsson, David Lynn, Derek Ernst and Lee Westwood on six under in fourth place.
Moore had a miserably 75 in the second round but put that firmly behind him with a 68 today, with birdies on the first three holes as well as the fifth and the seventh.
"I got off to a hot start," Moore told PGATour.com. "It was a pretty tough, blustery, windy day and the course is playing long.
"So you had a lot of long irons, hybrids and even fairway woods into the par fours. So obviously to get into a off to a hot start like that was great.
"I found myself in a little bit of trouble on the back nine and kind of started missing some fairways but I was able to scramble and keep it a reasonable round."
Ernst and Westwood could not match their form of the opening two days but scrapped their way to rounds of 72 to stay in contention two shots from the summit.