Fox opted for Testaverde over David Carr, who also got in a full week of practice.
Both quarterbacks have suffered through injuries, with Testaverde battling a case of Achilles tendonitis and Carr slowed by a bad back. The sense entering the week was that, unless his Achilles flared up again, Testaverde would get the start.
"He's made it through the practices fine," Fox said. "And I couldn't say that a week ago. So that's good for us and good for him."
Fox stopped short of naming Testaverde the long-term starter, citing the injuries his team has had at the position this season. Regular starter Jake Delhomme is on injured reserve after undergoing so-called Tommy John surgery to repair his right elbow. The Panthers were struggling offensively with Delhomme in the lineup, and haven't been able to find much rhythm without him.
Testaverde, who turned 44 earlier this week, might be without star wide receiver Steve Smith, who missed a third straight practice Friday with a shin injury. The Panthers won't make a determination on Smith's status until Sunday morning.
In three starts, Testaverde has completed 45 of 81 passes for 441 yards. He has just one touchdown pass and one interception, and a passer rating of 70.0.
Carr has also started three games, but his arm strength clearly has been reduced by the nagging back injury. The top overall choice in the 2002 draft, Carr said his back was much better during practices than in recent weeks, but Fox still decided that Testaverde would be the starter for the game against the Packers.
The Panthers are one of two teams in the league this season to have already used three different starting quarterbacks.
Senior writer Len Pasquarelli covers the NFL for ESPN.com.