Did UCLA upgrade at its most important position?

It was a question worth asking given what Ty Dieffenbach did Saturday in his first career start with the Bruins.

Making the right reads, throwing with precision and continually eluding pressure, the backup-turned-starting quarterback put on a dazzling display at the Rose Bowl in keeping his team’s unbeaten season rolling.

While it might sound like an insult to suggest that a backup could be better than Nico Iamaleava, Dieffenbach’s performance during the No. 12 Bruins’ 17-7 victory over Wisconsin indicated that, at the least, his team should be in good hands the rest of the season.

After replacing the injured Iamaleava midgame last week, Dieffenbach starred from the opening drive and made the big throws his team needed, especially with its run game bottled up for the first time this season.

The Calabasas Kid completed 22 of 33 passes for 264 yards with no touchdowns and one end-of-the-half interception to make the Bruins (6-0 overall, 4-0 Big Ten) bowl eligible at the season’s midpoint.

Of course, they have far bigger aspirations than that now that they’re the only remaining undefeated team in either the Big Ten or the SEC.

Dieffenbach could help UCLA reach the College Football Playoff for the first time in school history given the kinds of plays he made against the Badgers (4-2, 2-1).

Facing a third-and-5 in his own territory early in the fourth quarter, Dieffenbach found wide receiver Semaj Morgan streaking over the middle for a 34-yard gain. The Bruins eventually scored on Anthony Woods’ 3-yard run to surge into a 17-7 lead.

That was one of few successful runs for UCLA on a night it was held to a season-low 120 yards on the ground.

But the Bruins’ defense showed up in a big way for a third consecutive game. Highlights included a fourth-down stop midway through the fourth quarter that gave them the ball back with 8:10 left in the game.

Dieffenbach completed his first five passes, including an impressive 29-yarder to Landon Ellis along the sideline. He showed no jitters, exhibiting poise in the pocket and continually escaping a ferocious pass rush.

Dieffenbach also unveiled some dazzling moves on the ground, including a 360-degree turn away from a defender, while getting sacked just once.

With Wisconsin clogging the running lanes and daring Dieffenbach to pass, he happily complied while helping the Bruins convert seven of their first eight third-down opportunities.

On third-and-5 at the Wisconsin 22-yard line midway through the second quarter, Dieffenbach connected with tight end Jalen Saint Paul on a 21-yard reception. Operating out of the wildcat on the next play, running back Wayne Knight took the snap, waited a beat for an opening and plowed into the end zone to put the Bruins up 10-0.

UCLA’s defense was equally impressive, holding the Badgers to 123 yards by halftime. Wisconsin had difficulty sustaining drives after converting only one of its first six third-down chances and trailed 10-0 at halftime in part because it missed a 46-yard field goal.

It never really got any better for the Badgers.