Kevin Wilson abruptly resigned Thursday morning not even a week after leading Indiana football to bowl eligibility for a second consecutive season.

IU Athletic director Fred Glass announced the news at the Henke Hall of Champions in the north end zone complex of Memorial Stadium. Glass cited "philosophical differences" between he and Wilson that seemed to emerge in the time since Wilson signed a contract extension through 2021 in January.

"There is no smoking gun or single precipitating event that led to where we are today," Glass said. "I think it's really a realization by myself and Kevin that we're not on the same page with key ways in which the program needs to be led."

IU defensive coordinator Tom Allen was announced as Indiana's next permanent head coach not even a year after Wilson hired him. Glass said he and Wilson agreed to a split at 8:30 a.m. Thursday and that he met with Allen at 10 a.m. to offer the head coaching job without a contract yet formally written up.

"It's hard to believe," Allen said. "This day has been an absolute whirlwind. Unbelievable."

By beating Purdue last weekend to claim a fourth consecutive Old Oaken Bucket, Wilson became just the second head coach at Indiana to lead a team to multiple bowl games. He was the longest-tenured coach since Bill Mallory, the other coach with multiple bowl appearances at IU, and owned a 26-47 record in six seasons in his first head coaching job.

Wilson agreed to a six-year contract extension Jan. 11 worth $15.3 million shortly after leading Indiana to its first bowl since 2007. Many around the program believed next year's team would be even better than the 2016 version that went 6-6 thanks to plenty of players returning on both sides of the ball.

But at some point between signing his contract extension and his resignation Thursday, Wilson tarnished his relationship with Glass beyond repair.

Glass didn't speculate on the specifics of what he and Wilson disagreed on but revealed that an independent law firm investigated reports of Wilson allegedly pushing injured players to return ahead of schedule. That search found nothing out of the ordinary, Glass said, and the resignation was unrelated.

"I know this issue about medical has come out," Glass said, "and the reason I can speak so confidently that we don't have any medical issues and that our medical care has been so robust is that the outside group found that to be the case."

As part of the terms of resignation, Wilson will earn his one-year base salary of $542,000 to be issued over the next year.

Player reaction to Wilson's firing has been mixed. Some celebrated while others were quick to defend the now former head coach of Indiana football.

"I owe everything to Coach Wilson," former IU offensive lineman Ralston Evans said. After suffering severe leg injuries, Evans was unable to play his final season of eligibility in 2015 and instead joined the staff as a player coach at Wilson's suggestion.

Mitch Ewald, who was statistically the greatest kicker in program history, called Wilson "the best thing to ever happen to IU football."

He added that plenty of other former teammates he was in contact with, many of whom voiced their displeasure on Twitter, agreed.

"Go ask Adrian Peterson if he's thankful for the way Kevin Wilson coached. Sam Bradford," Ewald said, referencing Wilson's time as Oklahoma's offensive coordinator. "He knew how to read his players. He was a mastermind at figuring out what kind of coach he needed to be to specific players and becoming that coach to get the very best out of them with the player not even knowing that it was happening. He was a great man, a family man. He never once had bad intentions with his team."

Wilson was brash and didn't like to filter himself. When he was made about something, he was mad. When he was happy, he was happy. When players could be better, he said they could be better.

That honesty, former IU cornerback Tim Bennett said, made Coach Wilson who he was.

"He took this program from the mud his way," he said. "Now it's somewhere you'd actually want to go."

Despite a realignment of power and the shock that comes with it, Glass said he still believes Indiana football is moving forward. He made sure to credit Wilson for making that possible.

He suggested that Allen could be the "secret sauce" for taking Indiana's program to the next level, breaking through that perennial "door" that Wilson oftentimes mentioned.

Allen plans to continue to run IU's defense much like Wilson ran the offense during his tenure and will address potential coaching changes only after IU's upcoming bowl game.

"I'm very blessed to be the head coach of the Indiana University football program," said Allen, who described himself growing up a lifelong Hoosier fan in New Castle, Indiana. This was the type of job he dreamed about.

And he's taking it in place of the man who made it possible.

"My heart breaks for him,” Allen said. “I never expected this to happen."

MESSAGE BOARD: Discuss Kevin Wilson's dismissal here.

HELMHOLDT: How Kevin Wilson changed recruiting culture at Indiana

SOCIAL MEDIA: Reaction from current players, commits on Twitter

STORY: New IU Head Coach Tom Allen shares his vision for the future

STORY: Fred Glass and others weigh on on potential mishandling of medical situations