Jason Kokrak opens up five-shot advantage at AT&T Byron Nelson

Jason Kokrak fired a round-of-the-day 62 to open up a commanding five-shot lead after the second round of the AT&T Byron Nelson.

Kokrak, without a top-10 finish all season on the PGA Tour, posted eight birdies in a blemish-free display at TPC Four Seasons to pull clear of the chasing pack.

Billy Horschel is Kokrak's nearest challenger on seven under after finishing his round with three consecutive birdies, with world No 1 Dustin Johnson in the group a further stroke off the pace.

Jason Day birdied three of his final five holes to move inside the top 20, while Texas native Jordan Spieth missed cut after carding an ugly quadruple-bogey late in his round.

Beginning the day two strokes off the pace, Kokrak birdied the first and rolled in from 15 feet at the third to move into a share of the advantage.

The world No 128 posted a two-putt birdie at the seventh and picked up a shot at the ninth to reach the turn in 31, before pulling clear of the chasing back with back-to-back gains from the 12th.

Horschel briefly moved within three of the lead after his treble birdie finish, only for Kokrak to leave himself a tap-in at the 16th and post a seven-foot gain at the next.

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The American then missed the final fairway and pitched from the rough back on to the fairway, before getting up-and-down to maintain his bogey-free day.

Overnight joint-leader James Hahn temporarily got to seven under after following a gain at the sixth with an eagle-three at the next, only to bogey his penultimate hole to join the group on six under.

Cameron Tringale, Bud Cauley, Jhonattan Vegas and Byeong Hun An join Hahn in a share of third, with Johnson also six off the pace following a final-hole blemish.

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