Jason Kokrak earned a record lead at the AT&T Byron Nelson as two-time major champion Jordan Spieth sensationally missed the cut.
Kokrak was the star performer on Friday after carding an almost flawless eight-under-par 62.
The American's performance saw him move five shots clear to 12 under atop the leaderboard - the greatest 36-hole lead at the PGA Tour tournament since David Love III's four-stroke advantage in 2000.
Billy Horschel (65) is second heading into the weekend, but world number one Dustin Johnson is lurking in Irving, Texas.
U.S. Open champion Johnson posted back-to-back 67s to be tied for third at six under following the second round.
Teeing off on the back nine, Johnson was flawless as he birdied the 18th before adding another three consecutive birdies from the fifth to the seventh at Four Seasons Resort and Club Dallas.
Johnson would have been five shots adrift had he not bogeyed his final hole.
An Byeong-hun (66), Cameron Tringale (68), Bud Cauley (67), overnight leader James Hahn (70) and Jhonattan Vegas (68) are also six under.
Former world number one Jason Day is nine shots behind Kokrak following his second-round 69.
Masters winner and defending champion Sergio Garcia posted a five-under-par 65 to be two under through 36.
However, it was a day to forget for Spieth after he farewelled the tournament.
Spieth fired a five-over 75 with a quadruple-bogey nine on the par-five 16th hole as he missed the cut for the third time in four starts.
Spieth was well inside the cut line before the implosion that forced him to re-tee twice.