U.S. Open leader Johnson taking nothing for granted

After putting himself in a great position to challenge for a second U.S. Open title, Dustin Johnson was unwilling to get carried away.

Dustin Johnson took the clubhouse lead at the U.S. Open on Friday   -  Getty Images

Dustin Johnson was taking nothing for granted after assuming the clubhouse lead with his second round at the U.S. Open on Friday.

While much of the field struggled in damp conditions at the tricky Shinnecock Hills, Johnson carded a three-under 67 that left him at four under for the tournament.

The world number one dropped his only shot of the day at the first – his 10th – and capped a strong round with a 45-foot birdie putt at the par-three seventh.

READ: Johnson takes a two-shot lead as Tiger treads water

With fellow overnight leaders Russell Henley and Scott Piercy tumbling down the leaderboard and Ian Poulter yet to tee off when Johnson left the ninth, the 2016 champion was in a commanding position.

"I usually don't have any trouble sleeping. But, there's still a lot of golf left. There's still 36 holes left no matter what position I'm in," said Johnson.

"Going into tomorrow, I'm going to stick to my game plan, stick to trying to play the holes how I have the first couple days and see what happens."

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"I like being in the lead for sure. It's less shots you've got to make up. But, right now, I'm in a good position going into the weekend."

"I don't know if I'll have the lead or not. There's still a lot of guys out there that are playing. But, I'll be in a good position going into the weekend for sure."

Hefty gusts buffeted the players in Long Island on Thursday, while persistent rainfall posed a different challenge to those who went out early the following day.

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"The conditions were completely different. Yesterday was warm, windy, but it was dry. The ball was going pretty good. Today it was still breezy, but with the rain coming down and it was cooler, the golf ball was going nowhere," added Johnson.

"The course played really long. And it definitely played tough again, especially this morning, through our first 13 or 14 holes, it was playing very difficult."