Jimmy Walker leads by one stroke at the halfway stage of the Valero Texas Open in San Antonio.
The 36-year-old sunk successive birdies at the sixth, seventh and eighth to reach the turn in 33.
Further birdies followed at 10 and 14 before Walker dropped a shot at the 17th, to drop back to five-under-par.
However, Walker, a member of the US Ryder Cup team at Gleneagles last year, picked up a stroke at the last to card a 67 and lead by one from Charley Hoffman and Aaron Baddeley.
Jordan Spieth is a further shot back after a second round of 69 put him in contention heading into the weekend.
