Colt Knost is the halfway leader after shooting a five-under-par 66 on the second day of the RBC Heritage in South Carolina.
While Knost on nine under held a two-shot lead over Carl Petterson, Luke Donald made the cut at two over with a two-under round of 69 as he looks to retain his world number one slot.
The Englishman needs to finish in the top eight at Harbour Town to remain ahead of Ryder Cup team-mate Rory McIlroy in the standings.
He struggled to a four-over-par 75 yesterday but improved early today with three birdies in a bogey-free first seven holes. He finally dropped a shot at 15 though, leaving him six shots off the top-eight finish he needs.
Knost started the day in a three-way tie for the lead with Chad Campbell and Vaughn Taylor.
The American made an ideal start with birdies at the first two holes before finishing a bogey-free round with five birdies overall.
Petterson hit three consecutive birdies, and seven in total, as he followed up yesterday's 70 with a 65 although it could have been even better if he had not bogeyed the 15th.
Boo Weekley and Harris English were a further shot back after rounds of 66 and 68 respectively while Campbell (70) had slipped to a tie for fifth with Robert Garrigus (66).
Taylor hit four bogeys in his 73 to slip to a tie for 16th.
Defending champion Brandt Snedeker hit a 67 today to sit four under in a tie for seventh, with England's Gary Christian one stroke back following his 68.
Golf - PGA Tour (PGA)
Player Par Hole Colt Knost -9 0 Carl Pettersson -7 0 Boo Weekley -6 0 Harris English -6 0 Robert Garrigus -5 0 Chad Campbell -5 0 Rory Sabbatini -4 10 Kevin Na -4 0 Bob Estes -4 0 Brandt Snedeker -4 0 View complete leaderboard...
