Look at the 2019 national leaders in most any defensive category, and it was littered with Big Ten teams. There were 7 in the top 25 of total defense; 8 in the top 27 of yards per play; and 5 in the top 25 in points allowed per game.

Ohio State’s star-studded unit ranked near the top of just about every defensive category — not surprising considering it had the first 2 defensive players taken in the NFL Draft.

How will the conference fare on that side of the ball in 2020? After the Big Ten had 11 defensive players drafted in the 1st 3 rounds (2nd only to the SEC), naturally there are some concerns. Here is the biggest concern with each Big Ten defense, in descending order of total defense ranking:

Ohio State: Does it remember what it’s like to play without a generational pass rusher?

The Ohio State defense has gotten used to a certain luxury: Playing with a generational pass rusher. Since 2013, Ohio State has had a top-3 NFL draft pick lined up on the edge. Joey Bosa, Nick Bosa and Chase Young struck fear in opposing quarterbacks week in, week out (save for a game here or there, like Young’s suspension vs. Rutgers). Though Nick Bosa left the team after getting hurt in 2018, Young’s emergence vaulted him into a future 1st-rounder.

Even when that trio wasn’t getting sacks, opposing offenses had to allocate 2 or 3 players to stop them. That makes the rest of the defense’s job much easier. Maybe Zach Harrison — the No. 12 overall recruit in the 2018 class — takes a big step forward in 2020 and winds up in that same category as the Bosa brothers and Young, but he’s not there yet.

And because of the Buckeyes’ outsized expectations, one other thing is worth mentioning. Ohio State never rebuilds, it reloads — this much we know. But that will be especially challenging in a year with a pandemic ruining much of the offseason, where new roles are established. The Buckeyes lose 7 of their top 10 tacklers from 2019 and 4 of their top 6 pass rushers. With a conference-only schedule, the Buckeyes will have some fresh (albeit very talented) faces that need to get acclimated quickly.

Wisconsin: Does a drop-off in pass rush mean a drop-off overall?

It’s hard to nitpick too much with Wisconsin’s defense. In the past decade, it has finished in the top 20 nationally in total defense 9 times. And 7 times, it finished in the top 10. The Badgers have it rolling under defensive coordinator Jim Leonhard.

My major concern this year is the pass rush. The Badgers return all but 2 starters, but they were 2 stars in Zach Baun and Chris Orr. They combined for 24 of Wisconsin’s 51 sacks, which was 2nd in the country.

The lone “down” year for the Wisconsin defense in the past decade was in 2018, when it allowed 344.2 yards per game (29th nationally). The Badgers had just 19 sacks that season (110th nationally). So what happens if Wisconsin can’t replicate those lofty sack numbers? Is another down year ahead? The good news is the Badgers return a ton of production up front and in the secondary, plus safety Eric Burrell and linebacker Jack Sanborn will be 2 of the conference’s top players.

Minnesota: Winfield’s absence felt too much

It was hard to watch a Minnesota game last season without Antoine Winfield Jr. making some sort of big play. The 2nd-round NFL Draft pick led the Golden Gophers in tackles (83) and was 4th nationally with 7 interceptions. And while that was all well and good during Minnesota’s breakthrough season, it leads to questions for 2020 — especially considering the Golden Gophers bring back just 5 starters on defense.

Coney Durr is back to lead the secondary, and Winfield’s replacement — sophomore Tyler Nubin — is 1 of the highest-rated recruits on the roster. But without a star like Winfield, it’s hard to imagine Minnesota finishing in the top 10 in total defense again.

Michigan: The famed Viper position is a major question mark

Defensive coordinator Don Brown looks for his most versatile player to play the Viper position, which is part safety/part linebacker. Whoever is in that role has to be able to drop back in coverage, rush the passer and stop the run. It’s where Jabrill Peppers became a Heisman candidate and 1st-round pick.

Khaleke Hudson, who was manned the role the past 3 years, was drafted in the 5th round, meaning Brown is on the hunt to fill that void. The leading candidate is Michael Barrett, a former high school quarterback.

Michigan looks like it will be very good everywhere else on defense. The line is loaded, as is the secondary. If the Wolverines can find a good fit at Viper, it could have 1 of the top units in the country. But that’s a big “if” right now.

Iowa: Replacing A.J. Epenesa won’t be easy

As college football fans surely know by now, A.J. Epenesa was special — a former 5-star recruit who could have gone anywhere but chose to go where his father played. Don’t let the fact that Epenesa somehow slipped all the way to the No. 54 overall pick in the draft take away from his incredible impact in Iowa City. Just look at the final game of his college career, when he abused USC’s 1st-round pick, Austin Jackson, on his way to 2.5 sacks and a forced fumble in Iowa’s 49-24 win in the Holiday Bowl. The Hawkeyes finished in the top 12 nationally in total defense the past 2 seasons with Epenesa leading the charge.

Iowa lost 3 starters from the defensive line, including Epenesa. That unit is the biggest concern of what could be another top 25 defense. That’s because the Hawkeyes have solid depth everywhere else, and the presence of Chauncey Golston (the lone returning starter on the line) certainly helps. Golston needs to take his game up another level, though, as does Northern Illinois transfer Jack Heflin.

Michigan State: Mel Tucker doesn’t quite have the horses yet

Mel Tucker can coach defense, we know this. The first-year Michigan State head coach was a defensive assistant on national-title winning staffs at Ohio State and Alabama, and he darn near won another as the defensive coordinator at Georgia.

But that doesn’t mean the Spartans’ defense is going to be a defensive juggernaut right away. Look at his 1st season with Colorado. In 2019, the Buffaloes finished 104th in total defense.

The cupboard is far from bare in East Lansing, but Michigan State did lose a lot from a solid — though underachieving — defense. And as has been stressed in most stories you read, being a 1st-year coach in a pandemic is going to be extremely challenging. It’s going to take time, and that’s fine because no one is expecting miracles out of Tucker in his 1st season.

Northwestern: Opposing QBs could have all day

All things considered, Northwestern had a very good defense in 2019. With how terrible its offense was just about every week, finishing with a top 25 defense was admirable. Moving forward, though, Pat Fitzgerald might need to get creative.

The Wildcats were already a pass-rush challenged team in 2019, registering just 24 sacks (11th in the Big Ten). They lose Joe Gaziano, the program’s all-time sacks leader, and return no one who had more than 3 in 2019. Quarterbacks could have all day to throw against Northwestern in 2020.

Penn State: Leaky secondary

You might be surprised to know that the only B1G team to allow more yards through the air than Penn State in 2019 was Maryland. That’s not great company for a team that purports to be a College Football Playoff contender. Indeed, no B1G team had more passes attempted against them than the Nittany Lions, which is a sign they were leading for the majority of games. But you know who else was playing with a lead in every game? Ohio State, and it still led the Big Ten in pass defense.

This is an area Penn State really needs to clean up if it wants to make a run at the CFP. Winning games is great, but in college football, everyone knows that isn’t always enough. When you have 1 loss and are vying for a CFP spot, giving up late touchdowns to make the scores closer matters.

Indiana: Leaves the offense no margin for error

Indiana has come a long way defensively, and allowing 352.2 yards per game is nothing to scoff at, considering the Hoosiers routinely ranked as 1 of the worst defenses in the country earlier in the decade. But the defense left the offense almost no margin for error in numerous games. It was a breakthrough season, Indiana’s best in decades, yet it very easily could have been another 4- or 5-win season.

The Hoosiers allowed 589 yards against Purdue — and won. They allowed 514 yards against Nebraska — and won. Indiana was 1 of 9 teams in the country to allow 514 yards or more and win twice. So while the Hoosiers are improved, they could stand to make things a little easier on the offense.

Nebraska: Can’t stop the run (part I)

The Huskers’ defense has been a letdown in the Scott Frost era. Nebraska finished 12th in the B1G in total defense in 2018 and 10th in 2019. To make matters worse, it returns just 5 starters.

After allowing 188 rushing yards per game, Nebraska lost 3 linemen to the NFL. It doesn’t seem reasonable that the backups are going to step up in 2020 and improve upon that. The worst-case scenario is Nebraska tries to play fast on offense and fails to sustain drives, thus putting its defense on the field for too long.

In order to beat the beefy offensive lines trotted out by Wisconsin, Minnesota and Iowa (the 3 contenders in the Big Ten West Division), Nebraska needs to stop the run.

Illinois: Turnovers don’t come in bunches anymore

Takeaways are one of the hardest things to predict from year-to-year. Fumbles, especially, can be flukey. So will an Illinois defense that ranked 4th nationally in takeaways be able to replicate that in 2020? The Illini weren’t a great defense statistically in 2019, so will it get even worse in 2020 if they force fewer turnovers?

Rutgers: Offense’s poor performance will drain defense

Rutgers was the flip side of Illinois and the takeaways in 2019. Only Kansas and North Carolina State forced fewer turnovers than the Scarlett Knights (10). First-year head coach Greg Schiano has a defensive background (he was most recently the defensive coordinator at Ohio State for 3 years), and defensive coordinator Robb Smith was the DC for Rutgers in 2012 when it was 4th nationally in points allowed (14.2 per game). They actually have some decent talent returning, but the concern here is Rutgers is so bad on offense that even if the defense gets a few stops, it will be right back on the field after 3 plays, and the dam will eventually break. Inevitably, Rutgers is going to rank near the bottom of the Big Ten in most defensive categories even if its defense isn’t half bad.

Purdue: Can’t stop the run (part II)

My concern for Purdue is the same as it is for Nebraska. When you play in the West Division, teams like Wisconsin, Iowa and Minnesota are going to maul you with size up front. Purdue allowed 192.5 rushing yards per game in 2019, which was 12th in the B1G (and only 10 yards from being last). Let’s hope Purdue gets this fixed so it is in more pass-rushing situations, which would mean we get to see rising star George Karlaftis in action.

Maryland: Transfers have hurt depth, and defense continues to be young

Maryland’s last-ranked defense was young in 2019, sure. But it’s hard to make that transition to a more experienced unit when players keep transferring and are replaced by young guys. The secondary alone had 7 players transfer, including 2 former 4-star recruits in Deon Jones and Ken Montgomery Jr. Second-year coach Mike Locksley has done a good job on the recruiting trail, and now he needs to make sure those guys stick around.