COLUMBUS — The usual 100,000 or more fans weren’t there to see it but that provided no cover for Ohio State’s defensive backfield after it was set ablaze by Indiana quarterback Michael Penix Jr. last Saturday.

Penix passed for 491 yards and five touchdowns when Ohio State hung on for a 42-35 win after leading by four touchdowns early in the second half.

The fans still wanted to know what went wrong even if they didn’t see it in person. The media searched for explanations. And on Tuesday, Ohio State coach Ryan Day and defensive coordinator Kerry Coombs said they were also looking for answers before Ohio State (4-0) plays at Illinois (2-3) on Saturday.

The big plays OSU allowed, including four passing plays of more than 50 yards, occupied a front-row seat when Day analyzed the breakdowns.

“The glaring issue was the big plays. One of the things about this defense is that it’s designed to avoid big plays,” Day said on a Zoom conference. “The idea of this defense is to make you work your way down the field. There were a few things there we have to get fixed.

“I’d rather not get into too many details at this point but we have to get a couple things changed,” he said. “The issues here were all in the pass game and they’re correctable. It’s not like we can’t correct them. I know that we have the right scheme, now we just have to go do it.

“I like what we’re doing. I think we have the right stuff in. We just have to execute it a little better. If we do that I think we’re going to be in good shape.”

Coombs, like Day, was most alarmed by seeing Indiana get so many big plays.

“I think, first of all, we have to fix the big plays. There is no question about that,” he said. “Those four plays in particular are egregious so when you watch those it doesn’t make you feel good.

“There were a lot of good (defensive) plays but there is no doubt the focus is on those ones that didn’t go well. Those are the ones that have gotten our attention this weekend. They are fixable errors that have to be fixed.”

Shaun Wade, the only returning starter in the defensive backfield, Sevyn Banks and Marcus Williamson have been the starting cornerbacks in OSU’s three-cornerbacks alignment. Marcus Hooker has been the starting safety.

If Ohio State would make a lineup change, players like Tyreke Johnson, Ryan Watts and freshman Lejond Cavazos, who has not played yet because of an injury, might get more playing time at cornerback and Josh Proctor might play more at safety.

A coach putting a young, inexperienced player on the field takes a great deal of trust, even more so at defensive back, Coombs said.

“It’s easy to sub defensive linemen and let them get experience but it’s much harder on the islands of the secondary to do that. We’re practicing a lot of depth but we’re not playing a lot of depth. That (giving young players game experience) is something we’d like to do this Saturday. We’ll see what happens.”

The defensive backfield’s problems somewhat overshadowed the fact quarterback Justin Fields also struggled against Indiana when he threw three interceptions, two of which came after bad decisions he made.

“He was his own worst critic. He was really hard on himself. That’s what makes him great,” Day said about how Fields reacted to what was probably his worst game at Ohio State. “You can’t make bad plays worse and that did happen a little bit in the game. He knows it.”

Day could relate to his quarterback’s tough day. He threw five interceptions in a game when he

played quarterback at the University of New Hampshire and had four passes picked off in another game.

“When you’re being aggressive and you’re a throwing offense when something like that happens you have to play your way through it,” Day said.

“What you can’t do is all of a sudden get tight. You have to kind of work through those things. That’s really the first time Justin has had to do that. That’s the only way I know how to do it. You just keep playing through it. A 3-point shooter in basketball who is in a little bit of a slump just has to shoot his way through it. It’s the same in baseball.

“When those moments happen you just have to erase what just happened. That’s not easy. I had those games but you learn from them and move on,” Day said.