one thing to note on John Mateer, while it's true he's a veteran senior QB, he's only started 13 games in his collegiate career including the one last week.
2 of those starts were vs FCS teams, 8 of those starts were vs Mountain West teams, and only 3 have been vs P4/formerly P5 teams: Texas Tech (B12), Washington (B1G), and Oregon State (Pac 2). He's never started a game vs a ranked opponent nor a top 25 total defense. Of the three starts he's had vs P4/P5 opponents- Texas Tech was the #126 total defense last year (there are only 133 teams), Oregon State was the 98th ranked total defense last year, and Washington was the #28th ranked total defense last year.
Mateer was 17 of 34 (50% completion) passing for 245 yards and 1 TD vs 1 INT in a close win vs Washington.
He was 9 of 19 (47% completion) passing for 115 yards and 1 TD vs 1 INT in a big win over Texas Tech. Not a great day passing but he did happen to torch them on the ground with 21 carries for 197 yards and 1 TD.
Last but not least he was 17 of 23 (73.9%) passing for 250 yards and 2 TD's with no interceptions in a loss to Oregon State. By far his best day stat wise passing- but in a losing effort.
I have no doubt he'll be playing with better talent at OU at WR and whatnot- but this is the first legit defense he's going up against in his entire career. Michigan was ranked in the top 10 in total defense last year, is returning a ton on defense and right now SP+ ranks them the 4th best defense in CFB. And OU right now might be having issues with RB/OL and run game- which doesn't bode well for helping a QB out- puts a lot of pressure on the QB to be flawless to win a game if the run is non-existent.
this game really is one of the most interesting matchups all year- lot of unknowns for both teams.