Phil Mickelson has made a rally at the BMW Championship to share the lead at Indiana with Vijay Singh at the end of Saturday's play.
The 42-year-old took centre stage on the third day of the championship with a career high, with 10 birdies in an eight-under 64 to join Singh on 16-under.
Singh, who carded a round of 66 to to lead the tournament on Friday, struggled in the latter stages of play on Saturday and was eventually forced to share the top spot with Mickelson.
The 49-year-old Fijian mixed two birdies with three bogeys over his final five holes, including one at the last, to settle for a three-under 69.
Briton Lee Westwood got a four-under 68 and will head into Sunday's final round at at the Crooked Stick Golf Club alongside world number one Rory McIlroy (69), one stroke adrift of the leaders.
