Over-quarters means a 3-technique defensive tackle set to the strong side of the offense (determined as opposite the back or with the TE/H-back) backed by some variety of cover 4 (quarters coverage). Most teams are using split field coverages these days (as Gary Patterson has done forever) so they can mix in one variety of cover 4 to one half the field and another to the other half.
Perhaps the best and most common combination you see in football these days is for the defense to play the nickel/sam linebacker and boundary safeties as the force defenders but to ask them to play with depth and a touch of hesitation before they crash towards the line of scrimmage so they don't get burned by run/pass option plays like inside zone mixed with a bubble screen:
Different schemes and formations will call for different defenders to take on the roll of serving as the extra defender that isn't accounted for by an offensive blocker, but for most Big 12 teams most of the time that +1 defender against the run is that boundary safety.
The ideal +1 player can play with depth but still cover ground and make tackles near the line of scrimmage. He needs to be able to tackle in space but he also needs to be big and sturdy enough to fill the alley against a power back. This player needs to be either really smart/instinctive or have good COD (change of direction) so that he can handle everything on his grocery list in terms of coverage and where he fits against a given run scheme. Finally, this guy needs to have enough burst and power to blast through the wash to make tackles in traffic.
Typically a guy of 200 pounds or more, good downhill acceleration, fearlessness, and the hips to break down in space is going to be the best at executing in this role.
Here's a ranking of the best +1 defenders in the Big 12 heading into the 2016 season:
No. 1: Denzel Johnson, TCU
6-2, 210. Senior
2015 season: 79 tackles, 13.5 tackles for loss, 2 sacks, 1 interception, 8 pass break-ups
Gary Patterson always develops hard nosed safeties that play the run well and are physical enough to allow the defense to get away with having smaller personnel on the field. His "strong safety" position is really more of a nickel spot and always plays around the box.
Whereas for most other teams I'm listing the boundary safety as the +1 defender, the Frogs much more regularly involve their nickel/strong safety in that role, especially with Denzel because he's a great run defender. Johnson is excellent at forcing the edge, filling cutback lanes with lateral quickness and power, and he's totally at home playing in the box or blitzing.
Derrick Kindred was one of the better defenders in the Big 12 conference but when the Frogs can put more of a coverage-minded defender at that free safety spot behind Johnson they'll be really tough to beat.
No. 2: Jordan Sterns, Oklahoma State6-0, 200. Senior
2015 season: 108 tackles, 1.5 tackles for loss, 2 interceptions, 3 pass break-ups, 1 forced fumble
Sterns is more or less the standard for the position in the Big 12 and can regularly make tackles at or near the line of scrimmage playing at 10 yards deep or so. Sterns excels playing as a rover that spends most of his time reading flow and attacking the ball or the QB's eyes and he has the strength and short area speed to reach the ball and avoid the wash.
He's not a sensation but he's tailor made for this role and has been a dependable tackler with 100+ tackles each of the last two years plugging away in Spencer's defense the last two years. He's like Orion Stewart but better in the run support role of this position whereas Stewart is better in the coverage elements.
No. 3: Kendall Adams, Kansas State
6-1, 217. Redshirt sophomore.
2015 season: 41 tackles, 3.5 tackles for loss, 1 sack,
Adams was my favorite recruit in the 2014 K-State recruiting class and it seems the staff likes him quite a bit as well. He was pushed into action last year as a redshirt freshman due to injuries and is now the frontrunner to play opposite Dante Barnett for the 2016 Wildcat defense.
Due to youth and inexperience, the Wildcats were not their typical selves on defense last year and were prone to the kinds of errors in leverage and fundamentals that will gift offenses easy yards. Normally that's not the case at all and they can be defeated only through superior talent. However, if K-State can find a corner and a good tackle to add to the party next year and get back to playing great team defense in 2016 then they will be excellent on defense.
Kendall Adams is a big reason for this as he's both big and powerful but also rangy and fast. He's one of the few legitimate 4.6 safeties in this league and that speed allows him to play with the kind of safe depth that Snyder loves while still reaching the ball close to the line of scrimmage. The better he understands Big 12 offenses and where his help is in the Wildcat defense, the better he's going to become.
No. 4: Ahmad Thomas, Oklahoma6-0, 215. Senior
2015 season: 75 tackles, 1.5 tackles for loss, 1.5 sacks, 3 interceptions, 3 pass break-ups
Thomas is going to be transitioning in 2016 from playing more as a deep man to getting involved near the ball thanks to the Sooners' move to more of a 3-3-5 nickel approach. Both Thomas and his partner Steven Parker will probably spend some time as the extra man in the 8-man front but at 215 pounds this is more in Thomas' wheelhouse.
He should be quite effective here as he has some nice burst closing on the ball as well as the size to bring down backs and receivers even when they have some momentum. His experience and size combined with a more prominent role than "drop deep and clean up what Striker leaves behind" could result in some bigger numbers this year.
No. 5: Jah'Shawn Johnson, Texas Tech
5-10, 180. Sophomore
2015 season: 85 tackles, 4.5 tackles for loss, 2 interceptions, 3 pass break-ups, two forced fumbles
You'd like your enforcer and free-hitter in the middle of the field to be a big, intimidating player but Jah'Shawn Johnson has a lot of fight and he's pretty ferocious. He was the best run-support DB on the Tech roster last year as a freshman and they got into real trouble when he wasn't on the field.
As a sophomore playing behind a more experienced front and with a year of Big 12 play under his belt he could be quite good. Again, it's a hard life bringing down power backs when you're only 180 but with the right amount of fearlessness and leverage it can be done and Johnson brings that to the field. If this pup ends up reaching 190 or 200 then his bite will be really nasty.
No. 6: Kyzir White, West Virginia
6-3, 215. Junior
Some of his JUCO highlights look like extra footage from "the Longest Yard" and include some forearm shivers that could have knocked some people out. He's just a big, nasty guy that should thrive in the moderate amounts of space that he'll find himself in when playing in their schemes.
A 6'3" 215 pound savage that can move like this is worth his weight in gold in the Big 12 where defenses are often faced with the challenge of getting more speed on the field without going soft.
No. 7: Kamari Cotton-Moya, Iowa State6-1, 205. Redshirt junior
2015 season: 40 tackles, 2.5 tackles for loss, 1 pass break-up
Cotton-Moya had a really promising freshman campaign in 2014 and was expected to break out in 2015 but suffered an injury that cut his season short. Also notable, in 2015 the Cyclones moved to a 3-4 defense that put more of the run-support responsibilities on the outside linebackers while using the safeties either in coverage or as "check deep, then fill alley" defenders. It essentially worked like the Katy Tiger weak eagle defense but without the same measure of effectiveness.
He doesn't have quite as much burst as you'd like but he's similar to Orion Stewart in that he's a versatile player that can do a lot of things pretty well and he also brings more power to bring people down in traffic. One thing Paul Rhoads was always good at in Ames was finding and developing 2nd tier players like this that could be effective if positioned well.
If Iowa State could line him up for kill shots more consistently he'd be a menace. In 2016 he'll probably spend more time down in the box again while also playing in the deep 1/3 and as a deep 1/2 guy.
No. 8: Orion Stewart, Baylor
6-2, 205. Redshirt senior
2015 season: 64 tackles, 1.5 tackles for loss, 1 sack, 1 interception, 3 pass break-ups, 1 forced fumble
I assume Hall will replace Stewart after he graduates but then Baylor will have only gotten one good scholarship year from the former four-star. You have to wonder if the Bears will tinker and find a way to get them on the field together. I'd certainly be experimenting to see how Stewart holds up in their cover safety role where Chance Waz was less than inspiring a year ago (although Waz was quite good in run support). You don't want to take Orion off the field, because he's a legitimately good football player, but they could get more out of that position if they had a more intimidating physical presence.
Another possibility is that with another year of S&C and a healthier season, Stewart is even better against the run in 2016 and proves he belongs much higher on this list.
No. 9: Jason Hall, Texas6-2, 215. Junior
2015 season: 51 tackles, .5 tackles for loss, 2 interceptions, 2 pass break-ups, 1 forced fumble
Hall has great size for the free safety role at Texas at 6'2", 215 pounds, but he's never proven to be very instinctive or aware of how to make the best use of his size. He was fourth on the team in tackles a year ago and is in danger of losing his job in 2016 to young pups like DeShon Elliott or Brandon Jones if he can't make more of the opportunities presented in Texas' schemes for wreaking havoc.
That said, Hall has had a signature knockout blow in each of the last two seasons and is only just now entering his junior year. As a freshman he met Samaje Perine in the hole and drove him off his legs and into the ground. As a sophomore he met Joe Hubener in the hole and seriously reduced the impact from the Wildcat QB run game for the rest the contest with the blow he delivered.
No. 10: Tevin Shaw, Kansas
5-11, 206. Redshirt senior.
2015 season: 65 tackles, 1 tackle for loss, 1 sack, 3 pass break-ups
The Jayhawks were at their best in 2015 playing what I call "Aggro-6" which is cover 2 on the boundary and then an aggressive variety of cover 4 to the field that gets (usually) the nickel (sometimes the free safety) quickly involved in the run fits. The nickel was the man for the Jayhawks and that man was Tevin Shaw.
When your nickel is loosed on the edge in this fashion he can do a lot of damage, especially on blitzes where the offense doesn't always have him picked up. Shaw's compadre on the boundary, Fish Smithson, was the more effective edge blitzer while Shaw didn't add as much. It's not clear to me why K-State didn't just use a space-backer here to get more of a physical presence on the perimeter, I suppose their roster is rather limited.