Ian Poulter had Justin Thomas for company at the top of the leaderboard as he reached the turn on day three of the WGC-Bridgestone Invitational.
The Englishman had led by three strokes at one stage in his third round after firing back-to-back birdies at the second and third on Saturday.
But after getting into bunker trouble at the seventh, Ryder Cup star Poulter carded a bogey to drop back to 12 under par.
And World Number Three Thomas, who dropped shots at the third and fifth after taking advantage of the short second, bounced back with birdies at the sixth and eighth to join Poulter at the summit.
Northern Irishman Rory McIlroy, Australian duo Marc Leishman and Jason Day and American Kyle Stanley were two strokes behind the leaders on ten under.
Fellow halfway co-leader Tommy Fleetwood slipped back to nine under after reaching the turn in 37 as the South Course at Firestone Country Club firmed up to make things difficult for the world's best players.
