Adam Scott jumped into a tie for the lead after a 5-under 30 on the front nine, but with seven holes to play, Scott has a chance to do more than take the first-round lead. No player has ever carded better than a 63 in a major, something Scott could do on Thursday.
Scott would need to play the final seven holes at 3-under or better to set the record. He'll have a good chance to make up some of that ground at No. 12 and No. 13, as those are two of the three easiest holes on the course. Only No. 4 has yielded more birdies on Thursday than those two holes.
If he's unable to make up some ground there, Scott could also have a good birdie opportunity at the 16th and No. 18. He'll need to be close to perfect from here on in, and that includes navigating the difficult 17th. No. 17 has been the second-hardest hole in the first round.
Twenty-five players have shot a 63 during a major, including 11 in the PGA Championship. But despite several close calls, no one has ever been able to set a new mark. The most famous 63, of course, was fired by Johnny Miller at Oakmont in the final round of the 1973 U.S. Open.