Walker clear in Greensboro
America's Jimmy Walker fired an impressive round of 62 to take the lead in the Wyndham Championship in Greensboro.
The 33-year-old, who opened with a 66 on Thursday, enjoyed a bogey-free round of eight under par as he moved to 12 under, a shot clear of Webb Simpson.
US Open winner Simpson produced seven birdies in his round of 63, including four in the final five holes at Sedgefield Country Club.
Sergio Garcia also made real progress up the leaderboard with a 63 of his own, joining Harris English, Tim Clark and first round leader Carl Pettersson on 10 under.
America's English followed up Thursday's 66 with a 64, while South Africa's Clark was left rueing two bogeys in his second round 67.
First round leader Carl Pettersson, who started with a 62 of his own, hit two bogeys in his first eight holes on Friday but repaired the damage on the next two holes and an eagle at the par five 15th kept the Swede - a member at the club - in contention.
American duo Matt Every and Bud Cauley were nine under at the midway mark of the tournament, with fellow American Troy Matteson and Belgium's Nicolas Colsaerts a further shot back.
Elsewhere, in the final PGA event before the FedEx Cup play-offs, Tim Herron recovered from a dismal opening 76 by setting a new course record with a stunning nine-under-par 61.
The American began the second day lying 155th in the 156-man field, but surged up the leaderboard and into a tie for 41st place on three under.
Herron turned in 32 after four birdies and a bogey, before a birdie at 10 was followed by five in a row from the 13th as he posted 29 on the back nine.
Jamie Donaldson was the best placed of the British and Irish contingent in this event in North Carolina.
The 36-year-old Welshman added a 66 to his opening round 68 to join seven other players on six under - six shots off the pace.
Scotland's Russell Knox was two shots behind him, one clear of Gary Christian and two ahead of fellow Englishman Paul Casey.
Early contender David Mathias slipped off the pace, adding a 71 to his first round 63 - a triple bogey seven at the 11th doing much of the damage.
However, things improved slightly for South Korea's Sung Kang, who followed his opening round 80 with a more respectable 69.