This offseason, Ohio State gave defensive coordinator Jim Knowles a $1.9 million contract to bring the Buckeyes defense to a championship caliber.

Saturday night, Knowles will face his first true litmus test against Wisconsin.

That’s right. Wisconsin — which finished 88th nationally in total offense and 84th in scoring offense last season.

Even though the cast of characters from last season is largely unchanged, these Badgers might not be those Badgers. Like Ohio State, Wisconsin found outside help for the unit that cost it a trip to the Big Ten championship game a year ago, hiring Baltimore Ravens tight ends coach Bobby Engram to call the offense.

Saturday’s chess match between the 2 new coordinators will tell us a great deal about how much each team has strengthened its Achilles heel.

Ohio State defense showing progress under Knowles

It looked for all the world like Knowles could be anointed after just 1 game with the Buckeyes. Ohio State stifled Notre Dame in a 21-10 season-opening win. The defense, and not Ohio State’s high-octane offense, keyed the victory.

And then we saw Notre Dame’s offense play 2 more games. The Fighting Irish are more like the Punting Irish this season. So it turns out Ohio State’s defense simply did what others may be doing unto Notre Dame all year long.

Ensuing games against Arkansas State and Toledo don’t tell us much about Ohio State’s defense, either.

Some may be concerned that the Rockets broke 9 big plays against the Buckeyes (6 runs of 10-plus yards and 3 passes of 20-plus yards), but that is deceiving. Ohio State played without starting safeties Tanner McCalister and Josh Proctor. The Bucks were also without defensive lineman Mike Hall Jr., who was their most impactful defensive player the first 2 weeks.

Having Hall back on the field feels imperative against the Badgers.

As is often the case, Wisconsin boasts one of the country’s best offensive lines. And right behind them is one of the nation’s best running backs in sophomore Braelon Allen.

Allen is averaging 110.7 yards per game with 5 touchdowns. A year ago, he finished second in Big Ten rushing behind Kenneth Walker III — and he didn’t take over as Wisconsin’s starter until Week 5.

Simply put, Allen is the best offensive player Ohio State has faced this season.

How much has Engram’s arrival grown Graham Mertz?

Wisconsin’s biggest problem last season was that Paul Chryst wore a comical number of hats — head coach, quarterbacks coach and offensive coordinator.

That might work at, say, an FCS program. But even that’s a stretch. One might have to dive into Division II to find a coach successfully juggling that many responsibilities. Especially when the quarterback being coached was as erratic as Graham Mertz.

Mertz completed 59.5% of his passes for an average of 6.9 yards per attempt and 150.6 yards per game a year ago. He threw more interceptions (11) than touchdowns (10).

If Chryst was going to put in the time needed to make Mertz functional, someone else needed to call the plays. And Engram was the perfect candidate.

The former Penn State and NFL receiver brings an NFL perspective to an offense that desperately needed a jolt. Engram also gets to coach his son Dean, who moved from cornerback to receiver in the spring.

It’s too soon to be certain, but the new arrangement has Mertz looking like a new quarterback.

Mertz has completed 71% of his attempts, with his average skyrocketing up to 11.2 yards per attempt and 232.3 yards per game. He’s second in the Big Ten in passer rating behind only CJ Stroud. He’s also second in yards per attempt and fourth in completion percentage. A year ago, Mertz finished ninth in both of those categories.

But much like Ohio State’s defense, there’s a question of how much those numbers are bolstered by lesser competition.

Against Illinois State and New Mexico State, Mertz is 26-of-31 for 470 yards with 4 touchdowns and an interception. When Mertz faced Washington State, he was 18-of-31 for 227 yards with 2 TDs and an INT in a 17-14 loss.

We’ll learn a lot about whether Mertz is ready for prime time in a literal prime-time setting at Ohio Stadium.

Key matchup: Wisconsin offensive line vs. Ohio State defensive line

This is strength vs. strength.

When Hall is able to play, Ohio State has the deepest defensive line in the Big Ten. The Buckeyes face a Wisconsin offensive line that’s second only to Michigan in the B1G. (For what it’s worth, Ohio State is likely No. 3 in that category, so the Buckeyes D-line should be well-prepared in practice.)

And if it feels like Hall’s impact is being overstated here, rest assured that’s not the case. Notre Dame and Arkansas State combined to average 2 yards per carry when he was in the lineup. Last week, Toledo was able to scratch out 3.8 yards per carry in his absence.

That’s partially the result of Toledo having a dual-threat quarterback, which will not be a concern facing Mertz. But it also gives insight into why Hall’s nickname could be Dentures. He’s the teeth of the Ohio State defense.

Wisconsin will be hard-pressed to win unless it finds a way to take out the teeth. But the Badgers have one of the very few offensive lines that are capable of that surgery.