Jordan Spieth missed the cut at the Byron Nelson on Friday. Photo: Gary A Vasquez, USA TODAY Sports

American Jason Kokrak fired a flawless 8-under-par 62 to seize a commanding five-stroke lead midway through the AT&T Byron Nelson in Irving, Texas on Friday.

The 31-year-old Kokrak, who missed the cut at last week’s Players Championship, equalled the 36-hole tournament record at 12-under-par and put himself in position for his first PGA Tour with four birdies on each nine in following up his opening 66.

The stocky Kokrak may need the added cushion as the chasing pack includes World No 1 Dustin Johnson, who shot his second 67 to be 6-under on 134.

“All week I’ve been feeling better and better with the putter,” said Kokrak. “Dave Stockton Junior and his dad have helped me out the last few weeks, and things are starting to kind of go in an upturn.”

Billy Horschel, the 2014 FedExCup champion, was alone in second on 7-under 133 after a 65, with Johnson joined at 134 by South Korean An Byeong-hun (66), Jhonattan Vegas of Venezuela (68) and Americans Cameron Tringale (68), Bud Cauley (67) and James Hahn (70).

Johnson, who won three tournaments in a row before withdrawing from last month’s Masters after injuring his back in a fall before the opening round, said he is still working on regaining top form.

“Played a solid round,” said Johnson, who gave a shot back with a bogey at his last hole. “I made a lot of good shots and rolled the putter pretty nicely.”

Johnson said the back was no longer a concern.

“There’s no issues there,” he said. “Just need to keep practicing to get back. I had to take almost four weeks off, really didn’t practice. It takes a little time to get back in the form I was in leading into the Masters. It’s getting there.”

Jason Kokrak chips on to the 18th green during the second round of the Byron Nelson in Irving, Texas. Photo: Ashley Landis, The Dallas Morning News via AP

The cut was set at 2-over par, with 76 players advancing to weekend play.

One notable absentee will be local favourite Jordan Spieth, who shot 75 for 3-over 143, missing his second successive cut.

“Just disappointed,” said Spieth. “I’ve got to figure out what I’m doing on the greens, first and foremost. I’ve got to get back into rhythm there. Short game is just off (but) it’s close.”

The World No 6 will be defending his title at Colonial next week.

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