Bryson DeChambeau closed out his second round with a birdie to join Henrik Stenson at the top of the Arnold Palmer Invitational leaderboard on Friday as Tiger Woods struggled in his bid for a record ninth Bay Hill title.
After a scorching opening-round 64 Stenson's play stalled on another cool sunny morning at Bay Hill Golf Club in Orlando with the Swede reeling off 13 consecutive pars.
But with the pack threatening to push him out of top spot, Stenson, playing the back nine first, fired three straight birdies for a three-under 69 to leave him at 11 under at the midway point.
DeChambeau also had a big finish to his round, carding an eagle at the par-five 16th and joining Stenson when he hit his approach to within three feet at the 18th for an easy birdie to cap off the joint best round of the day, a six-under 66.
"It actually warmed up quicker than expected although it took a little bit longer for me to warm up," smiled Stenson.
Woods, an eight-time winner at Bay Hill and on the comeback trail after undergoing back fusion surgery last April, began the day four behind Stenson but was unable to keep pace, signing for a scrappy level-par 72 to slip seven behind the front-runners.
The 14-times Major champion was quickly in trouble on Friday when he sent his opening tee shot into the rough and had to settle for a bogey.
Despite the support of another large gallery, Woods was unable to get going, recording seven pars before making the turn with another bogey.
But the former world number one displayed some of his famous competitiveness on an error-free back nine, digging in and hitting back with two birdies to limit the damage.
Rickie Fowler, Rory McIlroy and Ernie Els remained in contention with gritty rounds.
Fowler battled his way to a one-under 71, enough to leave him headlining a pack of five Americans at six under.
McIlroy and Els, who was named captain of the International team for next year's Presidents Cup on Tuesday, were one shot further back on five under after returning 70s.