The WKU defense has a few question marks up front but returns much of the back seven that helped the Toppers rank No. 1 in total defense in the Sun Belt Conference last year.

The WKU linebackers and secondary are stacked with veterans, but the Toppers will face the task of replacing four 2012 starters on the defensive line.

New defensive coordinator Nick Holt said he’s looking forward to Saturday’s season-opener against Kentucky — if only to finally get a look at his defense in action.

“The biggest concern is really the unknown of us being in the fire with these kids the first time,” Holt said after Wednesday’s practice. “I’m sure they need to trust the coaches and the coaches need to trust the kids. I think that’s the biggest concern, just getting out there and relaxing and doing what we’re coached to do.”

The Topper defensive line is a big unknown to the players as much as it is the coaches. Senior Bar’ee Boyd and redshirt sophomore Gavin Rocker top the depth chart at defensive end, while redshirt freshman Devante Terrell and redshirt sophomore Bryan Shorter will hold down the middle at defensive tackle.

Things look a little clearer in the backfield.

Senior middle linebacker Andrew Jackson will hold down the middle of the field. The senior has led WKU in tackles in each of the past two seasons and was named a captain coming into this year.

Jackson, who will be flanked by senior outside linebackers Chuck Franks and Xa- vius Boyd, said the Toppers have spent a lot of time this fall looking at Kentucky’s offense and the offense that some of Kentucky’s new coaches have brought with them.

“We’ve just got to know everything so just in case they do come out and try to run something else we already know it, we went over it, so nothing will be new,” Jackson said. “We basically went over everything that they possibly could try to do.”

The WKU backfield — a group who nicknamed themselves “the Air Force” last season — also has plenty of experience.

Senior Tyree Robinson and junior Cam Thomas will run with the receivers as WKU’s starting cornerbacks. The duo combined for 95 tackles and three interceptions last season.

Seniors Arius Wright and Kiante Young will split time at free safety, while junior Jonathan Dowling looks to be the man at strong safety.

Dowling, a former Florida player who transferred to WKU, saw his first action last season. Dowling took advantage of the chance he was given, hauling in six picks and recording 68 tackles on the year.

While Jackson is the biggest name on the WKU defense, Holt said it’s going to take more than one person for the defense to match last season’s top performance.

“There’s a couple other ones that have got to do a good job of getting kids lined up in the first game and having that little calming presence in the huddle,” he said. “He’s huge, but everybody’s huge — whoever’s out there has got to play well.”