Andrew Putnam secured a one-shot lead at the halfway stage of the Shell Houston Open thanks to a seven-under-par 65 on Friday, and Padraig Harrington shot an impressive 68.
The 26-year-old Putnam was out in front, through. Yet to win on the PGA Tour, he made a solid start before six birdies in his last seven holes saw him snatch the lead from four-time major winner Phil Mickelson and Austin Cook.
"It's been a little bit of a struggle recently," Putnam said. "[I've] been working hard to get back and working on my swing, and the putter is usually there so just trying to get the ball on that green as fast as I can."
Harrington followed up his first round of 71 with a second-round 68 to end up five under, seven stroke off the leader.
Putnam had begun his second round in eighth after a first-round 67, and, although he was bogey-free through his opening nine holes starting from the 10th, was hardly making a move on the leaderboard.
However, a birdie on the par-three third - his 12th - proved to be the catalyst for a spectacular run. The 26-year-old played a brilliant approach to leave himself with a short putt for birdie and from there he did not look back. Three more consecutive birdies saw him surge up the leaderboard and, although he parred the seventh, he closed with two birdies to move clear of Mickelson.
Looking ahead to the weekend, Putnam added: "Golf is always a mental battle no matter where you're at. It will be an interesting challenge. I haven't been there before, so we'll see what it brings."
Mickelson began the round in fourth but fired a five-under 67 to move to 11 under and one off the lead.
The 44-year-old birdied the second, but a five on the third set him back. He then collected back-to-back birdies before closing the front nine with a birdie two.
Three birdies on the back nine followed, the highlight being a 22-foot putt on the par-five 15th, but a dropped shot on 17 meant the three-time Masters champion ended the day just adrift of Putnam.
"My short game has been sharp this week," Mickelson said. "I've hit some good pitches and touch. The putter does feel a lot better, but it's felt better for awhile. It's felt better for a few months now. I'm excited about this weekend."
Cook, starting at the 10th, had an up and down first nine holes, although a bogey at the par-four 11th was more than offset by three birdies. And he really found his rhythm as the round wore on, with five birdies on his final seven holes - including the closing four - lifting him to a superb 65 and a share of second spot alongside Mickelson.
Graham DeLaet (67) and Luke Guthrie (68) were a shot further back, while seven players - including the in-form Jordan Spieth - were nine under. Spieth, who has registered five top-10 finishes in eight outings this season, signed for a 66 on Friday.
