You have to look beyond that. UCLA was keeping a safety back to take away the deep ball and blitzing like crazy. Tanner took a few sacks because of that (which hurt is rating), but he stood in the pocket and took what the defense gave him which were the short and mid-range routes. It absolutely looked like Beck. He converted 3 third downs on a key drive in the 4th until Anae decided to run Nate Carter on 3rd and 5.

Keep in mind that Myles Jack was not hurt at the time was a force on D.

There's a reason that announcers and media were gushing about Tanner after that game. Far and away his most impressive performance. Sure, he's had better numbers, but those were against crappy teams. Mangum completely outplayed UCLA's frosh QB.