Quarterback Vinny Testaverde is listed as questionable for the Panthers' game Sunday against the New Orleans Saints.
He showed up for practice Saturday with a stiff back.
If Testaverde has to sit out the game, David Carr would likely start against New Orleans. Four days ago, coach John Fox had said the 44-year-old Testaverde gave Carolina a better chance to win.
Both teams are 4-6.
Testaverde had appeared to have recovered from a strained right Achilles tendon that forced him to miss a game and leave another at halftime. He had started the previous two games and practiced all week.
A team official says Testaverde was not injured at practice on Friday, but woke Saturday with back pain.
Fox said Wednesday that Testaverde would start ahead of David Carr, who has recovered from two concussions and a back injury.