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Although coach John Fox downplayed the seriousness of the situation, Carolina quarterback Vinny Testaverde missed practice on Friday when his sore Achilles flared up again, leaving uncertain the identity of the Panthers' starter for their game against the Atlanta Falcons on Sunday afternoon.

Testaverde, 43, had practiced on Wednesday and Thursday, experienced only minor discomfort and appeared ready to make his third start of the season. The 21-year veteran has been battling Achilles tendinitis for the past two weeks.

If Testaverde is unable to play against the Falcons, rookie Matt Moore, who wasn't even with the Panthers in training camp, would likely make his first regular-season start. Moore would be Carolina's fourth different starting quarterback this season.

In his two starts, Testaverde has completed 32-of-53 passes for 288 yards, with a touchdown pass and an interception. The Panthers were 1-1 in those two games. The Panthers will have a better determination on Saturday of Testaverde's status but might not make a decision on who will start until Sunday morning.

Carolina officially listed Testaverde as "questionable" on its Friday injury report.

"I wouldn't say it's a setback," Fox said after practice. "It's a little sore and we elected to rest him."

An undrafted college free agent, Moore, 23, was claimed on waivers in early September from the Dallas Cowboys. The former Oregon State standout has appeared briefly in three games and has completed 3-of-7 passes for 79 yards, with one interception.

Jake Delhomme, who opened the season as the starter, is out for the season after undergoing Tommy John surgery to repair ligament damage to his throwing (right) elbow. His primary backup, David Carr, started three games, including last week's loss at Tennessee.

But Carr suffered a concussion in that game, and while he has urged Fox to allow him to return to practice this week, the Panthers are taking a cautionary approach, and he has already been ruled out for the game against the Falcons.

If Moore started and Testaverde could not serve as the backup, the Panthers might be forced to elevate former UCLA quarterback Drew Olson from the practice squad. Olson was signed this week and has worked only a few days in the Carolina offense.

Len Pasquarelli is a senior NFL writer for ESPN.com.