Brock Spack is a football coach, not a mathematician.

But the way his team’s roster numbers looked over the past few weeks, continuing to play football this spring didn’t add up.

Down to a less than five healthy defensive lineman and with a roster 34 players lighter than in the fall, the Illinois State head coach and the Redbirds became the first FCS team in the country to opt out during the course of the spring season Sunday night.

“It was really a brutal decision to have to make,” Spack said during a Monday news conference. “It was disappointing, obviously. I’m heartbroken. But I’m responsible for this, and I know better. To continue would not be right.

“These (players) are someone’s pride and joy, someone’s child,” he said. “To put them in that scenario would be irresponsible. … I wasn’t going to do that to these kids. I watched this long enough. I won’t put their health and safety at risk any longer.”

ISU quarterback Bryce Jefferson said the team was disappointed by the news but understood the decision.

“All of us were really bought in to the spring season,” he said. “We trained all year. But we understand the reasoning behind it. It’s the smartest thing you can do.”

Spack, who announced the decision Sunday to players after discussing the situation with team leaders, said he was playing close attention to his defensive line group even before redshirt freshman Jude Okolo (concussion) and junior Jason Lewan (foot) were injured on the same play March 6 at Northern Iowa.

“I was holding my breath (before the spring) and Iwas praying,” Spack said. “Everything had to go perfect for us to pull this off, and it didn’t. When Jason and Jude went down on the same play, I said, ‘We can’t do this anymore.’ We played two more games after that and I was holding my breath up at North Dakota State and last weekend against Western Illinois.”

Lewan’s injury will force him to also miss the fall season, while Okolo has not played since being injured.

Southern Illinois head coach Nick Hill expressed disappointment at ISU’s decision. The Salukis were scheduled to play at Illinois State on April 3 in Normal.

The Missouri Valley Football Conference announced Monday that the remaining games on ISU’s schedule would be declared no contests. Therefore, ISU’s opponents will not receive a win.

“Look, we’ve all got injuries,” Hill said. “The transfer portal is open for every team in the country. To me, giving somebody your word, that means something. … We said we were going to play, and we’re going to play. Getting into the middle of the season and just quitting the season, I didn’t see that coming.”

SIU is among the Illinois FCS teams hit hardest by injuries. The Salukis are on their third starting quarterback. Hill said Monday that the team has lost two defensive tackles for the season and have two tight ends out with mononucleosis.

In addition, the Salukis had no reserves available in the secondary against North Dakota State.

“We’ve been through tough times,” he said. “I don’t know if teams can do this in the fall too, if they’re just having a bad season or if they get really decimated with injuries. I’m disappointed that we won’t get to play them.”

Spack said his team’s 1-3 record was not among the reasons for opting out.

“This is not about wins and losses,” he said.

Hill said he learned of the decision via text messages from an SIU athletic department staff member and athletic director Liz Jarnigan Sunday night.

“You probably found out before I did,” Hill said during his weekly news conference.

If injuries continue to mount, would Hill consider opting out?

“No,” he said.

Missouri State head coach Bobby Petrino was more blunt about ISU’s decision Monday.

The Bears were scheduled to host ISU in Week 1 before a winter storm caused the school to postpone the game, which drew criticism from Spack.

“Maybe their coach owes Missouri State an apology for the fact we couldn’t play a game because of snow and ice,” Petrino said. “He tried to pop off that we had some other underlying reasons, which is totally wrong.”

If Illinois State’s season had continued, senior defensive tackle Jake Powell said the expectations for his position group would have been overwhelming.

“Out of the guys we have left, the three or four of us, pretty much all of us are banged up,” he said. “From a workload standpoint, it was already getting tough. In practice, we don’t even have enough to go two deep anymore. In games, you’re really not rotating. So when you take more reps like that every game, you’re increasing the possibility of getting hurt.”

When asked what he wanted fans of ISU and the remaining teams on the Redbirds’ schedule to understand about the decision, Spack had a personal explanation.

“I’d tell them, ‘If this was your son, would you want him doing this?’” he said. “If your son was a defensive lineman here right now … would you want him to do this? Would you say this is worth the risk?”