Shane Lowry is five shots behind leader Sam Burns on two under after the second round at the Vivint Houston Open, while Padraig Harrington is one stroke behind the Offaly native.
Lowry carded a 69 for the second consecutive round in Texas to move into a tie for 14th alongside world number one Dustin Johnson, who shot a four-under 66 and fellow European major winner Francesco Molinari.
Harrington, meanwhile improved on his opening round by three shots to card a 68 and leaves the Dubliner on one under.
Graeme McDowell is three further back on two over after a 73, within the projected cut mark.
But it was Burns who jumped up to top spot of the leaderboard with a clean round of 65.
The American had three birdies across his first four holes as he opened up a two-shot lead.
Jason Day and Carlos Ortiz are tied for second after both following up their 67s with 68s, while Brandt Snedeker is among the five-strong group three shots off the lead.
Sergio Garcia, Henrik Stenson and Phil Mickelson all look set to miss the cut line, projected at three over.
The second round was suspended due to darkness, but Garcia sits five over after a poor opening 74, Stenson carded a 75 on Friday and sits seven over, while Mickelson is nine over after rounds of 76 and 73.