FORT LAUDERDALE, Fla. -- A stomach bug has made its way through part of the Ohio State football team. Head coach Urban Meyer said Monday about four or five players -- none of them starters -- have been quarantined, and the hope is that this is just a 24-hour type of virus.

If only the Buckeyes' defense could heal that quickly.

Ohio State's defense sure looked sickly in its last two games, against Michigan and Michigan State. If things don't turn around before Friday's Discover Orange Bowl, Clemson's high-powered offense could leave Buckeye Nation feeling ill again.

The defense will try to get well despite missing some important pieces. Cornerback Bradley Roby, who will be badly needed to help slow down Tigers star receiver Sammy Watkins, is dealing with a bone bruise in his knee that he suffered in the Big Ten title game. Meyer said Roby "practiced a little" on Monday at Nova Southeastern University, but Roby's status remains uncertain. Starting defensive end Noah Spence, the team's top pass rusher, still hasn't joined the team as he deals with a personal issue, and the Buckeyes are preparing Jamal Marcus and Steve Miller in his absence. Starting linebacker Curtis Grant is still dealing with back and ankle injuries that continue limiting him.

Not good news for a defense that's already had its share of problems.

"We've not been up to the standard," Meyer said. "It hasn't been the standard for a while."

Meyer said he's evaluating "the scheme, the development and the personnel" to try and figure out why the defense hasn't performed at a typical Silver Bullets level. But he said one thing he isn't considering changing is Luke Fickell, the co-defensive coordinator who calls plays on that side of the ball.

"I have a tremendous amount of confidence in Coach Fickell," Meyer said. "We're going to get this thing fixed."

Fickell met with the media at a press conference on Monday and pledged to keep plugging away.

"I'm not going to sit here and make excuses and say, 'Well, this hurt us,'" Fickell said. "The reality is we know we've got to play better. We know we've got to get better at the things that we do."

Meyer said he has given a lot of thought and spent much time already contemplating who will replace safeties coach/co-defensive coordinator Everett Withers, who is taking the head coaching job at James Madison. While Meyer didn't rule out changing some roles with the new hire, he said the next assistant will likely hold the same title.

The biggest immediate changes on the defense involve some new faces. Vonn Bell, a highly-touted 2013 signee, will get his first start at nickel back, with Tyvis Powell moving to safety. The play of the safeties was a big problem against Michigan State, and the Buckeyes have had trouble replacing Christian Bryant, who was hurt in the Big Ten opener against Wisconsin.

Should Bell have played more earlier?

"I've always been a big Vonn Bell guy," Meyer said. "It takes time to move him into the lineup. We had good chemistry, won a lot of games. But he's certainly a talented guy who's going to play a bunch for us."

Powell has only practiced "some" at safety this season, Fickell said. It's a risk playing two guys in two new positions against Clemson's dangerous receivers, but Ohio State is banking on ability.

"Vonn brings a little something different," defensive lineman Michael Bennett said. "He's a little jack rabbit. He's a little different. Tyvis has a lot of range at safety. I'm excited to watch them play Friday."

Fickell said Miller hasn't really practiced at Spence's end spot all season, and his lack of experience there could "make us maybe have to limit some of the things we do there." Marcus has spent time in that position and brings some good things to the table.

"He's going to bring some aggressiveness and some twitch and some fire to the edge," Fickell said. "But it's that test of time in front of 75,000 people on Friday night. If you have a new guy out there, how do they really, truly react and respond in front of that with those lights on?"

There are a lot of questions hanging over the Buckeyes defense heading into Friday's game. They sure hope to make a miraculous recovery.