First came the silence.

Myles Jack got his sixth carry of the game, and he started running.

He shook off a tackler or two, or three, or four, and kept running, and running, and running.

Then came the disbelief.

Almost in unison, a wave of incredulity took over Arizona Stadium.

Such was the reaction to UCLA’s fabulous freshman.

The linebacker-turned-running back broke a 66-yard touchdown run early in the fourth quarter, after getting major offensive playing time for the first time, in UCLA’s 31-26 win Saturday.

Jack finished with 120 rushing yards on six carries and, playing linebacker, added eight tackles and two pass breakups.

"I've been playing running back since I was a little kid," Jack said late Saturday. "After the first play in practice, I thought, 'I can do this.'"

Said quarterback Brett Hundley: "The nation saw what he can do with the ball." 

Offensive coordinator Noel Mazzone added Jack to the Bruins' offensive package last week, and unveiled his secret weapon Saturday. 

The results were breathtaking, almost as breathtaking as the Wildcats’ neutralization of UCLA star linebacker Anthony Barr. Widely considered the nation’s top NFL draft prospect at his position, Barr was held without a tackle.

Jack, who starred on both sides of the ball at Washington’s Bellevue High School, wasn't the only Bruin to make the big switch. 

UCLA used seven different defensive players on the offensive side of the ball — defensive linemen Cassius Marsh, Kenny Clark, Eddie Vanderdoes and Brandon Willis lined up on the offensive line, and defensive lineman Keenan Graham and linebacker Jordan Zumwalt lined up in the backfield in the team’s jumbo package.

“We’re not going to shy away from putting freshmen in there in tough situations,” coach Jim Mora said. “We’ve always talked about it; it’s just a matter of how much you give young players to do.”

Said Mazzone: "Those kids made us look like we know what the hell we're doing." 

Mazzone had to pull out all the stops against an Arizona defense that came up big regularly.

Not big enough, at times, as Bruins quarterback Brett Hundley proved on the game’s first play.

Hundley had a 66-yard touchdown bomb to Shaquelle Evans on a play that looked like it was setting the stage for a rout similar to last season’s 66-10 domination at the Rose Bowl.

But the Wildcats constantly brought pressure, and all of the Bruins’ creativity sometimes seemed for naught.

Only sometimes, though, as Jack proved.