Shane Lowry carded a second round 68 to lie just five shots off overnight leaders Byeong Hun An and Brendan Steele at the Waste Management Phoenix Open.
The Offaly man began the tournament with round of 69, but went one better after a strong back nine finish.
He picked up a shot at the third, but a wayward tee shot on the par-four fifth hole contributed to a bogey to cancel out the early birdie.
However, he picked up shots at the 10th, 13th and 17th to finish three under par for the round.
Pádraig Harrington carded an even par round of 71 to remain at one over.
Korean An and American Steele are the men to catch and both birdied three of the last four holes on TPC Scottsdale's Stadium Course to reach 10 under par in Arizona.
An, who shot to prominence when he won the European Tour's BMW PGA Championship at Wentworth in 2015, had six gains and a single bogey in his round of 66.
Steele had four birdies in a flawless 67, holing putts of 18 and 15 feet on the last two holes to snatch a share of the halfway lead.
Scotland's Martin Laird matched An's five-under-par round, making birdies from close range at the 15th and 17th after starting on the back nine.
Laird shares third place with first-round leader Matt Kuchar, Korean Sung Kang and Japan's defending champion Hideki Matsuyama.
US Ryder Cup star Rickie Fowler got one of the biggest cheers of the day when he whipped the 20,000 crowd around the 16th into a frenzy before firing a wedge to within a couple of feet, only to then miss his birdie putt.
A round of 68 was enough to give Fowler a place inside the top 10.
