On Friday, the 44-year-old signal-caller was listed as "probable" on the Panthers' injury report after missing his third straight practice.
Earlier this week, Coach John Fox said Testaverde has been experiencing general soreness.
He appeared fatigued in last Sunday's 37-6 thrashing by Jacksonville and his passes lacked zip.
He completed only 13 of 28 passes for 84 yards against the Jaguars before being replaced in the fourth quarter by rookie backup Matt Moore.
The Charlotte Observer reported Friday Testaverde has been bothered by a lingering Achilles' tendon problem since his first game with the Panthers Oct. 14 against the Arizona Cardinals.
Moore is Carolina's likely starter Sunday, but Fox said that move is a "game-time decision."