Sweden's Robert Karlsson opened up a three stroke lead after a blazing second round at the FedEx St Jude Classic in Memphis.
Karlsson, who was beaten in a play-off by Lee Westwood last year, stormed to the top of leaderboard at the halfway stage by following his opening round of 66 with a five under 65.
That helped the 41 year old to nine under and a lead of three shots over American duo Colt Knost and Keegan Bradley.
The home challenge did not end there though with John Merrick a further stroke back while Harrison Frazar joined another Swede, Fredrick Jacobson, on four under.
Defending champion and World Number Two Westwood endured a difficult day, highlighted by a double-bogey six at 12, as he carded an even-par 70 to leave him eight shots off the pace.
Karlsson began the round a stroke behind overnight leader David Mathis, who dropped back to three under after a round of 72, and the Swede shot ahead with four birdies in a flawless first nine.
The former Ryder Cup winner, who began his round on the back nine, then began his return home with birdie at the first and another at six had moved him four shots clear before his first blemish on the par-three eighth.
Karlsson's round of 65 was the equal best of the day, matched also by his countryman Jacobson and Frazar as they moved into contention.
