Fox said he thought up until the end that the Panthers would be able to rework Muhammad's contract.
"I thought there was a strong possibility," Fox said. "I know from our coaches' evaluation standpoint, it was something that was a priority. It just didn't work out."
Muhammad's numbers have fallen off sharply this year after a Pro Bowl season with the Panthers in 2004.
However, Muhammad still leads the Bears in receptions (38), receiving yards (474) and is tied for touchdown receptions (two). Those numbers pale in comparison to Steve Smith, who has 58 receptions for 937 yards and nine touchdown receptions through nine games.
Given the strength of both teams' defense, Sunday figures to be a low-scoring affair.
"I think it is going to be that type of game going in," Fox said. "Sometimes it's hard to predict how a game goes. I even go back to the Super Bowl. It was like two different games. The first half was a defensive struggle and the second half was an offensive shootout. Sometimes it's hard to predict exactly how a game is going to go. I like the way they're coached. I like the way they're organized in what they're doing, and I expect a very, very tough, hard-fought game."
However, Fox said he doesn't mind playing cold-weather games.
"The elements are big," he said. "That's kind of something that I've liked about football ever since I was a little kid. I don't know what the weather is going to be, but I don't think it's going to be 80 (degrees) and beautiful."
Overall, Carolina's defense is playing as well as any in the league.
The Panthers have forced 14 turnovers, recorded 19 sacks and scored two touchdowns off interception returns in the past four games.
"Our goal is to be the best defense we can be all-around in every phase," said linebacker Will Witherspoon, who returned an interception 35 yards for a touchdown against the Jets.
"We have stepped up our pass defense and our corners stepped up and made big plays. All around, the defense stayed together. ... We know as long as we stick together and play together, we can accomplish anything."
Coincidentally, the wind was whipping at Bank of America Stadium for Wednesday's practice. Working against that wind might come in handy this weekend in Chicago.
BY THE NUMBERS: 0 - Number of 100-yard rushers for the Panthers this season.
QUOTE TO NOTE: "A lot of people probably wrote us off at the beginning of the season because we started off slow, but we never gave up hope. I feel like we're one of the best teams in the NFL right now. That's what is scary about it because we are playing pretty good right now, but we can still get better. We still have not reached our peak yet." - Panthers cornerback Ken Lucas
INJURY UPDATE: Six players missed practice on Wednesday, including center Jeff Mitchell (hip), safety Thomas Davis (thigh), tight end Kris Mangum (knee), linebacker Vinny Ciurciu (back), running back Stephen Davis (knee) and safety Mike Minter (thigh). Stephen Davis and Minter are listed as probable, while the others are listed as questionable.
Mitchell's injury means rookie Geoff Hangartner likely will see more action in practice, but expect to see Mitchell on the field come Sunday.
However, don't be surprised to see the Panthers activate an extra offensive lineman on Sunday just in case Mitchell's knee begins bothering him.