Last Updated: 15/06/13 10:03am
Billy Horschel enjoyed a "great day" at Merion after defying a brutal layout to fired a superb three-under 67 in the second round of the US Open.
The American, who lifted his first PGA Tour title in New Orleans in April, rolled in his fourth birdie putt of the round at the 18th to take over the clubhouse lead from Luke Donald on one under par.
Horschel capped an opening 72 with a birdie at the 10th - his last - and he made a positive start to his second round as he picked up a birdie at the second before grinding out seven straight pars.
He broke the run with his second birdie of the day at 10 and added another at 11 before making his only mistake of the day at the 13th, but he finished in style when he converted another excellent approach to the last.
"It was a great day," said Horschel, who managed to hit all 18 greens in regulation. "Four birdies at a US Open. I'll take it. I wish I had a couple more, though.
"I didn't know I hit every green until I walked off 18. It's a cool thing, but it's not the first time I've hit all 18 greens. I've done it plenty of times in my career. Obviously it's at a US Open, but I think the softness of the greens helped that.
"Everything seems good. I've just got to stay patient and keep committing and executing every shot and I'll be okay on Sunday.
"Patience is something that has always been a struggle for me, but I'm doing a really good job of it this week, staying patient and just taking what's in front of me.
"If I do have a stretch of bad holes, it's not that I don't hit the panic button. I just don't press right away. I just think the older I get, the more mature I get on the golf course, the more understanding I have.
"I don't have as much patience as a lot of guys out here, but I've grown week in and week out.
"No matter how bad I hit it or how bad my short game is or how bad I'm putting during the practice round days, once I get to Thursday I flip a switch and find some way to play well."
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