Seamus Power carded a five-under 66 to sit five shots back from leader Chesson Hadley following the second day of the Palmetto Championship at Congaree in South Carolina.
Starting on the back nine, the Co Waterford native mixed in a bogey on the 17th with birdies on the 15th and 18th before coming home strongly with four birdies, including at the par-three fifth.
His 66 moved him to six-under and a share of fourth with Americans Harris English, Chez Reavie and Pat Perez as well as South Africa's Erik van Rooyen and Wilco Nienaber.
Hadley also shot 66 to go with his opening-round 65 to be 11-under overall, holding a two-stroke lead over world No 1 Dustin Johnson.
Hadley matched seven birdies with two bogeys on Friday while Johnson was tied for the lead through 17 holes before double-bogeying the par-four 18th to finish with a 68.
American Tain Lee, appearing in only his third PGA Tour tournament, also carded a 68 to sit third, four strokes off the pace.
Padraig Harrington finished with a one-over 72 to drop back to three over but missed the cut by two shots.
The three-time major winner began with a bogey on his opening hole at the 10th but rallied with two birdies prior to starting the front nine.
But a bogey on the first, followed by a double bogey on the fourth and a further dropped shot on eight was not mitigated by birdies on two and five.