Northwestern will play some cover 0, straight man on the backend with 3 underneath rat players. The 3 underneath defenders will not blitz but be responsible for zone underneath help. They play this in various situations on the field, but liked it especially in the red zone in 2020.
Here's a clear picture. They play cover 0 vs Iowa with 4 secondary players in man to man. The LB's have hook/curl and underneath help.
They played the coverage vs Wisconsin in 2020.They had success with the coverage and it was an integral part of their defense.
Clemson will play some 3 under technique with straight man coverage on the backend. It is an excellent philosophy to get man coverage on 3rd and short situations while getting the linebackers to help on some of the shallow crossing and mesh routes in those situations.
Some teams will run cover 0 without help but this technique gives you a 4 man rush with 3 underneath defenders.
101 and 25 min mark
Here are 2 examples of the concept vs Boston College in 2019
Oklahoma State was another team that utilizes the coverage under Jim Knowles. They play it with a mug look at times in 3rd down situations and as part of their base package.
Vs Texas Tech
3rd and 5
presnap cover 0 mug pressure look
post snap cover 0 but only blitz 4. The LB have zone underneath help as DB forcing everything to the inside. Most college teams will play with a free safety with this kind of look but Knowles is aggressive and plays it with zero middle of the field safety help.
Cover 0 with pressure.
vs Notre Dame
Mike Hankwitz brings a nice inside LB blitz with the safety with the DT dropping to the hook as a rat defender. They almost get the pick on the play.
Cover 0 same pressure vs Wisconsin
Northwestern vs Wisconsin
These are just some of the cover 0 concepts you will see at the college Level.