As the US PGA Championship heads into the weekend there is an unlikely name atop the leaderboard in Robert Streb, but the 29-year-old is not getting too far ahead of himself.

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Streb has just the one win on the PGA Tour since gaining his card in 2013, having won the 2014 McGladrey Classic, but that could all change if he can build on Friday's amazing score of 63, which propelled him into a two-stroke lead alongside Jimmy Walker at Baltusrol.

The American posted four birdies and a bogey as he teed off from the back nine in the second round, and played a tremendous nine holes to finish the round shooting four birdies – which really could have been five had he managed to sink his birdie opportunity at the eighth.

And while Streb was somewhat disappointed to miss his chance at the eighth, he was delighted to correct the error at the ninth and become the 28th player to shoot 63 at the major tournament.

"I was pretty excited about it. I was waiting on it to break, waiting on it to break and it finally turned there at the end. But it was a great round. Happy to be a part of that 63 club I guess," Streb said. "My putt on eight was fairly pathetic effort! But I made up for it on nine."

With wins in short supply, Streb admitted he has struggled with setting his expectations on the Tour.

"I just struggled with my expectations a little bit. Kind of thought I would keep it going, and it's been tough. Probably learned the hard way, you've got to start over again," he said.

"But you know, the ball-striking and the putting has been a little difficult this year and just been trying to hang on by a thread. Obviously it's coming together this week, which is nice."

And now that he is in a winning position, Streb is just aiming for consistency.

"I'm sure it will be busy, Saturday at a PGA. But just try to stick to what I'm doing. Try to do the same things we've been doing the last couple days, and hopefully it's good enough," he said.

"I've just kind of tweaked my swing a little bit, and I don't know a better way to put this, but it kind of feels like my golf swing again. May not hit it perfect or anything, but it kind of feels normal again. I don't feel like I'm trying to do everything I can to hit it straight. I can just kind of take a swing at it and catch it solid for the most part."