Indiana University officials conducted two investigations into former football coach Kevin Wilson's treatment of injured players, according to a report from the Indianapolis Star on Saturday.

Wilson, who resigned as Hoosiers coach Thursday over what athletic director Fred Glass called "philosophical differences," was initially questioned about his treatment of injured players in April 2015, according to the report. In April 2015, Glass hired an outside law firm to conduct the inquiry, and he did so again in the past four to six weeks, sources familiar with the second investigation told ESPN.

According to the Star report Saturday, the initial investigation was prompted by complaints about the IU football program's treatment of former lineman Nick Carovillano, who played for the Hoosiers in 2014. On April 8, 2015, Carovillano's father, Dean, contacted IU associate athletic director Anthony Thompson to make a complaint on his son's behalf. Six days later, according to the Star, IU retained a law firm to investigate the allegations.

Dean Carovillano told ESPN on Saturday that his son suffered a back injury in practice in September 2014. When Nick Carovillano asked an Indiana trainer to examine his back, the trainer asked him if he had numbness in his legs. According to his father, when Carovillano said he didn't, the trainer told him, "Then I won't treat your injury." A few days later, according to his father, Indiana's trainers told Carovillano that he was suffering from shin splints and needed to stretch better. But when Carovillano returned home to Cincinnati a few weeks later, his parents noticed he could barely climb out of his car.

A 2015 investigation found that ex-IU coach Kevin Wilson didn't improperly influence the team's medical staff in regard to injured player Nick Carovillano, but the investigation did find there was an "unhealthy environment for injured players." Michael Hickey/Getty Images

That weekend, a doctor noticed Carovillano struggling to walk across the room at a social gathering. The doctor told him he needed to stop playing sports immediately, according to his father. When Carovillano returned to Bloomington after the weekend at home, he told trainers a doctor advised him to stop playing. He was examined by Indiana's trainers and sent to a specialist in Indianapolis. The specialist diagnosed him with having bone fragments and three injured disks in his back.

"He'd been called every name in the book to keep practicing," Dean Carovillano said. "He was a 19-year-old kid. He wanted to please his coaches, not be ridiculed, and wanted to make the team."

After rehabbing his back for six months, Carovillano decided to leave Indiana in April 2015. When his parents drove to Bloomington to help him move out, Wilson and other IU coaches requested a meeting with them. They tried to persuade Carovillano to stay through the end of the semester so the team's graduation rate wouldn't decrease, according to his father.

"My son lost everything," Dean Carovillano said. "He lost his scholarship. He has an injured back, and he was an emotional wreck."

According to the Star, Glass met with Wilson on April 13, 2015, to discuss the allegations about his mistreatment of injured players. The next day, Glass sent Wilson a memorandum that included a warning: "As you know, IU will not tolerate any behavior among you and your staff that penalizes, ostracizes, or criticizes any injured football player. I trust that you and your staff are abiding by this long-standing policy."

According to the Star, the law firm Glass hired for the investigation interviewed 20 people and issued a 26-page report on May 1, 2015.

"An outside investigation has concluded that Nick did not receive inadequate medical care, that there is no evidence that the coaching staff exerted improper influence on the medical staff regarding the student-athlete's medical care," Glass wrote in a memo to Wilson, which was obtained by the Star. But Glass also wrote, "Even within the unique culture of football, there were behaviors that may create an unhealthy environment for injured players. This last conclusion was based on a variety of findings, including your own admission that you made jokes to injured players or implied that they are not useful members of the team.

"Some players said that they felt pressure or witnessed coaches pressuring others and indicated that they found it depressing and demoralizing to have coaches make such comments when they were already frustrated with their injuries. It was found that coaches appear to push players to work harder than they should when they have injuries that are unconfirmed by an outside test."

Even after conducting the initial review into Wilson's conduct, Glass rewarded him with a raise and a six-year contract extension -- at $2.55 million per season -- through 2021 after he guided the Hoosiers to their first bowl appearance since 2007.

During a news conference in Bloomington, Indiana, on Thursday, Glass said there was "no smoking gun, no precipitating event" that led to his decision to ask for Wilson's resignation. Glass said he was confident that no players' medical issues were compromised under Wilson. Instead, Glass said the two "weren't on the same page" in terms of leadership style.

Carovillano, however, wasn't the only former Indiana player to complain about Wilson's treatment of him when injured.

In interviews with ESPN this week, several former Hoosiers and/or their parents criticized Wilson's treatment of injured players and the medical care they received while playing for the team:

-- Mark Booth, the father of former Indiana wide receiver Dominique Booth, told ESPN that his son suffered a concussion in practice a week before the 2015 season opener. After sitting out a week, Booth was supposed to gradually return to workouts. But after a 20-minute workout one day, Booth was told to run six miles, according to his father. When Booth returned home, he vomited and suffered severe headaches.

"His symptoms went haywire," Mark Booth said.

Dominique Booth, who was ranked No. 225 in the ESPN 300 and the No. 2 prospect in Indiana as a senior at Pike High School in Indianapolis in 2014, received a medical redshirt and didn't play in 2015. The next spring, according to Booth's father, Indiana's coaches asked him to sign a medical waiver before he returned to the field, even though he'd been medically cleared to play. Mark Booth said his son declined to sign the waiver and asked to be released from his scholarship.

According to Mark Booth, IU medically disqualified his son to play without his consent. When they met with Wilson and other IU coaches this past spring, they were told Booth wouldn't be released from his scholarship.

"They held my son hostage," Mark Booth said. "Wilson said he couldn't release him because he was one of the best recruits he'd signed and it would hurt his recruiting base in Indianapolis."

-- Former Indiana cornerback Laray Smith told ESPN that when he had a bump on his back shortly before the 2013 season, IU trainers told him it was only a bruise.

"I'm a freshman, so I'm not thinking anything," Booth said. "I'll just listen to them. But it continued to hurt. I went to the doctor for a checkup and got an ultrasound. It was a blood clot, and they drained it and said, 'You're better now.'"

But after Smith returned to practice, the bump came back and was even bigger. He had surgery to remove the blood clot and returned to play in games a week or two later.

"I knew it was serious because it was a blood clot," said Smith, who left Indiana in July 2015 and now runs track at Delaware State. "Now that I'm older I know, but I wasn't thinking that way at 17 or 18. It's like, 'You're good, you're going to play as a freshman.'"

-- Former Hoosiers offensive lineman Bernard Taylor, who played under Wilson from 2011 to '14, told ESPN Radio's The Right Time with Bomani Jones on Thursday that Wilson's treatment of players "was ridiculous," but he didn't offer specifics.

"Don't get me wrong, he's a great coach and smart on the offensive side of things. But as far as the way he treated those cats, it was ridiculous," Taylor said. "If you really want to go on a whole list, a whole tangent, things beyond injuries, it's an entire list, and I'll be talking to you all day, man."

-- An unnamed former Indiana player, who was a member of the 2011 team, said players worked hard not to be included on the injured list because of the consequences.

"The trainers would hate to go up and tell him about injured players because Wilson would [curse] them," said the player, who requested anonymity. "Then he'd go into the training room and tell the players, 'No, you're going to [expletive] practice,' and, of course, the players would go practice."

The player said Wilson also ridiculed Indiana's players constantly for their poor play.

"As a human being and a person, he didn't treat people around the program with a lot of respect," the player said. "He cursed us up and down, and I'm sure that goes on [at] a lot of other places. But when someone is telling you from 6 a.m. to 10 p.m. every day that you couldn't play on Oklahoma's practice squad, it wears you down."

Staff writers Chantel Jennings and Jared Shanker contributed to this report.