The issues with Ohio State were absolutely scheme and technique, it was not personnel I don't know where you are getting that idea from.
So for the last few seasons, the defense was being coordinated by Kerry Coombs, he was our former DB's coach from Meyers stint in Columbus, but he left after the 2017 season to join the Titans. He returned to Ohio State in 2020 after Jeff Hafley went to BC. Most OSU fans were excited for him to come back as DC.
Well it turns out the defense was extremely basic for the last 2 seasons. No variety of pre snap looks on defense, it was the same 4-3 and 4-2-5 lineup across the board every single time, with no blitzes and man to man coverage 90+% of the time. Offenses (with talent) started to catch on and were able to attack the weak points. Think Alabama in the title game where OSU still trotted out 3 and 4 linebackers against Bama's excellent receiving corps.
Technique and fundamentals were terrible as well. Some of Ohio State's worst tackling and angles for a defense ever were on display the past two years. Corners never looked back for the ball either. Turnovers were rarely every forced. Coombs got demoted from being a DC after the week 2 Oregon loss and Matt Barnes takes over (safeties coach). It was like putting a piece of tape over a leaky pipe. Ohio State never really had an identity for the past couple of seasons on defense and it showed.
Enter Jim Knowles, excellent coordinator and play caller that turned Oklahoma State's defense into something special. They are an attacking defense, completely different from the bend but don't break, read and react defense that Ohio State had been running. Oklahoma State was among the tops in the country in turnovers, 3rd down conversation rate, run ypg, pass ypg, basically all the meaningful stats. His defenses have a lot of pre snap looks, he utilizes a DE that plays with a hand in the dirt and stands up behind the LOS creating a sort of 3-3-5 or 3-2-6 look. It's also a 3 safety look where the safeties don't stay in the same spot every snap. The defense blitzes a lot, linebackers get sacks in this defense, something Ohio State linebackers never got. Last year they had 2 sacks all season because they never blitzed, meanwhile Oklahoma State linebackers had 14 sacks on the year.
Lastly personnel. So Ohio State was also a really young team last year, one of the youngest in the country. They return a lot of talent and they are a lot more veteran now. I believe they return like 7 starters on offense and 7 on defense, but they rotated a lot (almost too much) and have a lot of quality depth on the team. You seem to imply that OSU has a talent problem if you're talking about personnel, but OSU is going to be one of the most talented teams in the country this year. Their 2020-2022 classes were all very strong, the 2021 class in particular had something like 6-7 five star players in it and they are now sophomores. I mean the starting DE duo is likely going to be 5* guys in Jack Sawyer and JT Tuimoloau, both sophomores. The rest of the defense is littered with 5*s and top 100 players. They bring back literally every DL and LB and DB that contributed anything to the defense last year except 1 DE and 1 DT and 1 Safety. Look at the past 3-4 recruiting classes if you want to see how much talent is on the team.
Also you mentioned that Ohio State's running game was mediocre last year, that is true. We have a talented RB but we could not run block last season. That was mainly due to the fact we played 4 true tackle bodies along the line, 2 at tackle and 2 at guard. Taller guys playing on the interior can't bend and generate enough leverage in the run game to excel and it showed. Well Ohio State fired their OL coach and replaced him with Justin Frye from UCLA who had good run games there. Apparently there was a riff between Day and our old OL coach (really lazy guy) on how they wanted to coach the OL in blocking schemes, well now the new guy will teach them and the OL is finally going back to having actual guard bodies on the interior. So naturally you would expect the running game to be better with a Heisman contender in the backfield.
And lastly, you mention that you think ND will run for 250-300 yards and you say that pretty confidently based on last year's results. While I don't think they run for anywhere near that much, even the run blocking is going to be changing on this team. So Ohio State's DL under Larry Johnson has always been an attacking one. You beat your man and tackle the ball carries. More work for the DL, less for the linebackers. But under Knowles it's the exact opposite. The DL walls up the OL, And the linebackers find the ball carrier and bring him down.
The whole defense is just fundamentally different, and there's nothing you can look at last year and try to exploit this season because it's just not the same. The Ohio State defensive coaches can't look at last year's tape on Jack Coan and then prepare for a mobile QB that's probably more likely to run than throw. Trying to blame all the failures on personnel is so very far from the truth, they are great talented players playing in a very shitty and basic scheme, often times out of position.
