Butler (ankle) was held out of Thursday's practice, although the defensive tackle did some work on the side. He was a limited participant Wednesday.
"Yeah, I guess you could say a setback," Rivera said. "I didn't react as we hoped it would have in the morning. They had him on the side moving. We'll how he is tomorrow morning."
Bradberry (foot) was limited for the second consecutive day, and the cornerback is making progress, although he hasn't yet pushed it 100 percent.
"It's feeling better every day," Bradberry said.
But he might not be fit to play against the Cardinals on Sunday.
"The biggest thing about it, obviously, is his movement," Rivera said. "We just have to make sure come Saturday morning when we get to our last walkthrough where we are with it. On Sunday we'll make the final decision."
Rivera said Daryl Worley and Robert McClain are in line to start Sunday's game if things remain "status quo." Worley (concussion) and McClain (hamstring) did not play against the Saints in Week 6.
"Daryl has done a really nice job," Rivera said. "We know Robert is a very steady player."
Cornerback Teddy Williams was a new addition to the Thursday injury report. He did not participate with a knee injury.
"He kind of felt something," Rivera said. "They are going to examine him."
Left tackle Michael Oher, meanwhile, remains out with a concussion. Rivera said he's checked in with Oher, who is getting better but remains in the protocol.
"He'll just continue in the protocol," Rivera said, "and we'll take it day-by-day, week-by-week."
View photos of the Panthers' week of practice leading up to their game against Arizona.