Brooks Koepka carded a four-under 67 to extend his lead to two shots going into the final round of the Open in California.

The 23-year-old, playing in his first PGA Tour event excluding majors, mixed six birdies with two bogeys to go 15 under overall, two clear of George McNeill and Jason Kokrak.

Koepka has more at stake than most - a win here would earn him full Tour membership.

Although relatively unknown in the States, he has done well on the other side of the Atlantic, winning a clutch of second-tier Challenge Tour events to earn his place on the full European Tour.

"Sixty-two, I don't know how it could ever not be fun" - George McNeill

And he showed that good experience with a solid third round, carding three birdies and a bogey on his front nine, then doing likewise on the way back - including birdies on the final two holes.

That was enough to put him two clear of Kokrak and McNeill, who had a day to remember as he equalled the CordeValle course record with a nine-under 62, mixing ten birdies with a single bogey.

"It was a lot of fun," McNeill told "Sixty-two, I don't know how it could ever not be fun.

"I figured out something on the range last night and my swing was much more comfortable today. I felt free so I could go ahead and aim at some flags. I pulled it off and made some putts."

One shot back at 12 under was Jimmy Walker, who also carded a 62, tying a record he already jointly held.

Alongside Walker were Vijay Singh and Robert Garrigus, while Japan's Ryo Ishikawa led a group of five on ten under.