Phil Mickelson shot a four-under-par 66 to tie for the lead with Brett Quigley after three rounds of the PGA Mastercard Colonial at Forth Worth, Texas.
A victory for Mickelson, who birdied the 18th hole from the fringe to tie, would make him the first player to defend his title at the Colonial Club since Ben Hogan 48 years ago.
Quigley, who won on the Buy.com Tour a week before tying for second at last month's Greater Greensboro Classic, matched Mickelson's 66 for a 54-hole total of 11-under-par 199.
Japan's Shigeki Maruyama is three shots behind the leaders after a five-under 65. David Toms, who defeated Mickelson by two shots earlier this month at the Compaq Classic, is tied with Tom Lehman and Rocco Mediate at seven-under 203.