Michigan State coach Mark Dantonio has stepped down from his position as the longtime coach of the Spartans program. Dantonio made the surprising announcement on Tuesday afternoon, less than 24 hours before National Signing Day takes over the college football world and just two weeks after receiving a longevity bonus from the university.

Defensive coordinator and linebackers coach Mike Tressel will serve as the team's interim coach.

The decision to step down comes at an interesting time. Dantonio is the subject of a lawsuit filed against the school by former Spartans staffer Curtis Blackwell, who is seeking more than $5 million in damages for wrongful termination. In the complaint, Blackwell alleges that Dantonio, who has spent the last 13 years at Michigan State, committed multiple NCAA recruiting violations.

Among the allegations are that Dantonio orchestrated employment for the parents of two Michigan State football players with the school's mega-donor Bob Skandalaris. Additionally, the suit claims Blackwell accompanied Dantonio on an in-home visit for a five-star recruit when Blackwell wasn't authorized to conduct an off-campus visit. Dantonio is serving as a witness in the case and refuted these allegations in a Jan. 10 deposition. Lawyers for Dantonio have called the allegations "not only false, but totally gratuitous."

Dantonio was asked if the lawsuit played a part in his decision during a press conference on Tuesday night.

"Zero," he said. "No relevance whatsoever."

Dantonio relayed the following statement regarding his decision on his Twitter account. It can be read, in part, below:

There have been so many amazing life moments in the last 13 years. When I reflect, I think of our Big Ten championship games, our Big Ten Championships, the big games, the playoffs, the bowl wins, the moments, the milestones, the graduates, the NFL opportunities and finally, and perhaps most importantly, the relationships made. This job has always been a 24/7, 365 day-a-year position. There is no down time and it is filled with the demands and challenges of managing games, players, coaches, recruits, donors, staff, media, an enthusiastic fan base and competition at the very highest level. I will miss it all but feel the sacrifices that I have made away from my family must now become my priority at this time in my life. My plan is stay on within the university and athletic department in a role involving special projects, especially transitioning our players, both current and incoming, to their next challenges. It has truly been an honor and a privilege to serve as the head football coach at Michigan State University. I will forever be a Spartan. Go Green!

Dantonio was asked during his press conference whether his enjoyment in coaching waned over the last few years. He did say that he still enjoyed it, but that the wave of non-football issues that came across his desk became tiresome.

"I was 50-50 on what to do and how to do it," he said. "In the end, if you're 50-50 on something, you need to be over here. This job demands 100 percent. It just does. I think everybody out there who's coaching would agree to that."

Dantonio recently received a $4.3 million longevity bonus from the university on Jan. 16, which came following the conclusion of his 13th season in East Lansing, Michigan.

During his tenure, Dantonio led the Spartans to three Big Ten titles, a College Football Playoff appearance and a school-best 114 wins. His Michigan State teams also went 8-5 against rival Michigan, including a stretch of seven wins over eight seasons from 2008-15.

Dantonio also orchestrated six 10-win seasons but was coming off of back-to-back 7-6 efforts in which he was widely criticized for refusing to make sweeping changes on offense with his assistants. In all, Dantonio finishes 115-57 at Michigan State with 12 bowl appearances in 13 seasons (6-6).

Michigan State has not yet announced a successor, but it is widely believed that Cincinnati coach Luke Fickell will be the top target. Check out the top candidates for the Spartans job from Dennis Dodd.