"The problem with mono is in some cases there is an enlargement of the spleen, and we don't know when he'll be back," Petrino said. "But we know he'll be out indefinitely."
Wilson, a Greenwood High graduate, has felt sick lately and has missed the past two days of practice.
Redshirt freshman Nathan Dick will serve as the backup quarterback for Saturday's game against Ole Miss in Reynolds Razorback Stadium. He's expected to keep the job for the immediate future.
Dick, who has yet to play this season, is the younger brother of starting quarterback Casey Dick.
"It's not like it's a big reach to put Nathan back as the No. 2 (quarterback) at all, but he's done a good job," Arkansas quarterbacks coach Garrick McGee said. "His attitude has been great the whole season. He's been into the game plan.
"So there's nothing that we're going to do that we have to step back for Nathan. He's caught up with everything."
Wilson has played in two games this season and completed 11-of-22 passes for 69 yards with one touchdown and two interceptions.
Running back Michael Smith spent 45 minutes doing individual work during Wednesday's practice. That gave Petrino a reason to be "encouraged" that the junior will play Saturday.
Smith has been bothered over the past few days with the effects of a concussion suffered in the fourth quarter of Saturday's 21-20 loss at Kentucky.
"I did see Michael (on Tuesday) night and he was feeling a lot better. He had some energy. He had been resting most of the day," Petrino said Wednesday morning. "But again, it's a day-to-day thing.
"He was confident (Tuesday) night that he would be able to practice (Wednesday), but certainly that's in the doctors' and trainers' hands."
Freshmen De'Anthony Curtis and Dennis Johnson and junior Brandon Barnett continue to get more reps in practice because of Smith's absence.
Smith, who's the Southeastern Conference's leading rusher at 131.8 yards per game, carried the ball 35 times for a career-high 192 yards and one touchdown in the Kentucky loss.
Arkansas cornerback Jamar Love has missed the past two games because of a broken thumb. But Love, whose right hand was still in a cast Wednesday, was on the practice field and defensive coordinator Willy Robinson didn't rule out the possibility he could help Saturday.
"(Tuesday) he came out and did (individual work)," Robinson said. "(Wednesday) he took some reps. We're not real sure what his status is right now. It might be just in case we need another guy.
"But the thing about it is, he came out there on his own. And yesterday we were surprised that he dressed. It was good that he did. He wants to be out there. So his reps might not be as a starter, but if there's an accident waiting to happen, he might be out there."
Cornerback Ramon Broadway started in Love's place against Auburn and Kentucky.
Usually, Arkansas' defensive staff breaks down film, finds an opponent's tendencies, defines their schemes and presents the information to players on a weekly basis.
Robinson said his players have had more input in the preparation this week because of their familiarity with Ole Miss' coaching staff.
"It's really interesting," Robinson said. "There was a couple of things they were able to help us sit down there and see how they break out of the huddle, what they're doing, recognizing things."
Arkansas chancellor David Gearhart doesn't mind if Razorbacks fans are yelling Saturday.
But Gearhart hopes Houston Nutt isn't booed by critics during his much-anticipated return to Fayetteville as Ole Miss' coach.
"I hope they don't boo him," Gearhart told The Associated Press on Wednesday. "I hope if there's any behavior like that, it's about wanting to win. I'm going to be right there yelling as loud as I can for us to win, but I'm hopeful that doesn't happen. If it does, I think it's going to a small minority."
Wilson Out Indefinitely
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