When Butch Jones made the move to part ways with defensive coordinator John Jancek and bring in Penn State defensive coordinator Bob Shoop, expectations for Tennessee’s defense shot through the roof. Shoop was widely regarded as one of the best defensive coordinators in the country after his work at Vanderbilt and Penn State, and he was expected to come in to Tennessee and push the Vols’ defense to the next level.

But through seven games this season, Tennessee’s defense has struggled to even be mediocre at times, especially over the last two games.

The Vols have given up a combined 1,186 yards over the last two weeks to Texas A&M and Alabama. Part of that can be explained by the absurd amount of injuries the Vols have sustained on defense, but those numbers are eye-popping regardless. And even before that, the Vols had struggled to stop lesser offenses this season.

After seven games in the 2016 season, the Vols are in the bottom half of the SEC in the majority of defensive rankings. The Vols are 10th in total defense (427.1 yards per game), 12th in rushing defense (219.4), 11th in scoring defense (29.9 points a game). and 6th in pass defense (207.7). Tennessee is also 13th in sacks (10), tied for 9th in interceptions (6), and 6th in opponent third down conversions (35.6 percent).

There are a lot of reasons why the Vols have failed to produce on defense this year. Part of it is just poor execution and certain units failing to live up to expectations. Part of it could also be put on coaching.

But those are just surface observations. And while they certainly have merit and have contributed to the issues for the Vols’ defense, other numbers help explain even better why Tennessee has struggled on defense this year.

First of all, there’s the obvious: Tennessee’ multitude of injuries. The Vols have lost at least four starters on defense for most or all of the season after their game with Alabama. Linebacker Jalen Reeves-Maybin, cornerback Cam Sutton, and linebacker Darrin Kirkland Jr. have all missed significant time, and only Kirkland Jr. is expected back any time soon. Defensive tackle Kahlil McKenzie is out for the season after tearing his pectoral muscle against Alabama. Backup linebacker Quart’e Sapp is also out for the season. And another full-time starter, defensive tackle Danny O’Brien, was kicked off the team prior to the Alabama game.

Throw in injuries to cornerback Malik Foreman, Micah Abernathy, and linebacker Cortez McDowell against Alabama, and you can see why the Vols had trouble stopping the Tide’s vaunted rushing attack.

Since the Ohio game, the Vols have been without Reeves-Maybin, Sutton, and Kirkland Jr. for all of SEC play. That’s a combined 83 starts-worth of experience the Vols have been missing in SEC play from those three players alone. And with both Reeves-Maybin and Kirkland out at linebacker, the Vols have had to play multiple younger players at both positions to find something that works (with the exception of junior Colton Jumper).

And when you add in those injuries and decimated depth to the amount of snaps the Vols have played on defense, you see an even clearer picture of Tennessee’s defensive woes.

Tennessee’s offense hasn’t done their defense many favors this year so far. The Vols have run 511 plays on offense this season, the 7th-fewest in the SEC. They also have the 7th-ranked scoring offense, averaging 30.4 points per game. This all means that the Vols have struggled to keep their offense on the field and produce points, meaning their defense has been on the field more often than coaches would like.

The numbers back up those feelings as well.

Opponents have run 519 plays against the Vols this season. That means the Vols have had more plays run against them than they’ve run themselves. It would be one thing if Tennessee’s normal defense was having that many plays run against them. But injuries have blasted the Vols’ depth, and that amount of time on the field has taken its toll.

Tennessee’s disappointing performance on defense so far this season is a mix of many different factors. But it can’t all be blamed on coaching, schemes, or players failing to live up to the hype. Injuries have ruined most of the depth the Vols had on defense, and the offense hasn’t been able to keep the defense off the field long enough to spell them.

If the Vols can get healthier down the stretch, some of these things will work themselves out. But these factors help explain why Tennessee’s defense hasn’t been as good as advertised thus far.