Mississippi State is reportedly in the market for a new defensive coordinator after word came out on Monday that Geoff Collins had accepted the same position at Florida.

Collins’ departure leaves a hole on Dan Mullen’s staff, although just a few weeks ago Mullen made it sound as if there were some serious fixes required on that side of the ball. While he won’t have to start over, there is rebuilding to do.

Mississippi State was one of the most aggressive defenses in the country this season under Collins’ direction. The Bulldogs finished second in the SEC in sacks, operating Collins’ “Psycho Defense.” While the Bulldogs were nasty inside the red zone, holding opponents to the lowest red zone scoring percentage in the country, there were some major issues on that side of the ball.

Chief among them: defending the pass and giving up massive chunks of yards. The Bulldogs were last in pass defense in the SEC by a mile and were ranked 107th in the nation (out of 128 teams) in pass plays of 20 or more yards allowed, ranking even lower in 30- and 40-plus yard plays.

Just a few weeks ago, Mullen slammed his defensive staff for those very issues after the Egg Bowl.

“That’s just absolutely pathetic,” Mullen said in his post-game press conference. “That’s a terrible job by our defensive coaching staff.”

After taking that public lashing, Collins saw fit to make a lateral move in the SEC to join Jim McElwain’s staff at Florida.

While Mullen was fed up with his team getting gashed over and over against Ole Miss, he likely didn’t have any plans to lose his coordinator. While State’s pass defense suffered in 2014, the Bulldogs were ranked fifth in the SEC in total defense in Collins’ first season, 2013.

Not only will Mullen have to replace his top assistant on defense, he’ll likely be replacing his two best players. MSU loses senior Preston Smith, who blossomed at defensive end this year, while middle linebacker Benardrick McKinney is almost certainly going to be turning pro. Those types of players aren’t easily replicated, and the new defensive coordinator will have to find ways to produce without that outgoing talent.

As Mullen negotiates a contract extension with Mississippi State athletic director Scott Stricklin, it’s fair to wonder if he’ll push for terms similar to what Ole Miss coach Hugh Freeze got in his extension last week: a bump in his assistant salary pool. Collins was a highly regarded and sought-after defensive coach, and for Mississippi State to maintain its lofty perch in the SEC West they’ll need to find a defensive coach just as talented.

That could mean opening the checkbook. Mullen’s assistants made $2.68 million combined in 2014, per USA Today’s coaches salary database. That ranked 12th in the SEC out of 13 reported salary pools (Vanderbilt is a private school and does not disclose salaries), ranking above only Ole Miss this year.

Mullen wanted improvement on defense; now, changes are being forced on him. With negotiations on an extension ongoing and Michigan reportedly interested, Mullen has a chance to force some of the changes he was pining for last month.