ESPN NFL

GREEN BAY, Wis. -- Understudy David Garrard only played two series, but that was plenty of time to upstage Jaguars' starting quarterback Byron Leftwich.

After the Jaguars' offense sputtered into the third quarter under Leftwich, Garrard came into to lead Jacksonville to a pair touchdowns and a 21-13 victory over the Green Bay Packers on Thursday night.

Having stated his case for a starting job on the field, Garrard couldn't hide his ambitions after the game.

"It's a little frustrating not being able to go into the season as the starter," Garrard said. "But as long as I can do my job and when my number's called, perform at the same level, that's what I'm here for."

Thanks to Garrard's two touchdown drives and a late interception return for a touchdown by Jaguars linebacker Brian Iwuh, the Packers (2-1) lost their unbeaten preseason record.

And now they have to hope they won't be losing Donald Driver for an extended period of time after the Pro Bowl wide receiver left the game with a foot injury just before halftime.

Packers coach Mike McCarthy said Driver's injury was initially diagnosed as a foot sprain.

McCarthy said he didn't have any reason to think Driver had a more serious fracture-dislocation that could sideline a player for months.

"He's in good spirits," McCarthy said of Driver. "So we'll have more information tomorrow."

Garrard opened with a seven-play, 46-yard drive capped by a 1-yard touchdown run by LaBrandon Toefield. After fumbling a snap on second-and-goal on his next drive, Garrard came back with a 25-yard touchdown pass to tight end George Wrighster to put the Jaguars ahead 14-10 late in the third quarter.

Garrard was 6-for-7 for 97 yards and a touchdown before he was replaced by third-string quarterback Quinn Gray, who played despite the death of his father Thursday morning.

Leftwich was 6-of-16 for 67 yards, often dodging pressure from the Packers' defensive line -- the Jaguars were missing two starting offensive linemen -- and overthrowing open receivers several times.

After an underwhelming performance in what is supposed to be a dress rehearsal for the season, Leftwich knows he might once again face questions about his ability.

"It's something I've dealt with from the beginning, and I'm quite sure I'm going to deal with it the rest of this year," Leftwich said. "But the main focus for us, you all know me, you can't begin to listen to all that."

Leftwich, who is entering his fifth season with the Jaguars, has missed 15 games over the past two seasons because of injury, including 10 last year because of an ankle injury.

Leftwich had surgery on the ankle, and came into training camp saying he felt completely healthy for the first time since his college days at Marshall.

Brett Favre and the Packers' first-string offense got off to a slow start. Favre was 14-for-20 for 130 yards and led the Packers to a field goal before he was relieved by Aaron Rodgers just before halftime.

Rodgers immediately led the Packers on a 9-play, 73-yard drive, ending with a 1-yard touchdown run by Jackson -- but losing Driver in the process.

Driver was injured after catching a pass from Rodgers late in the second quarter and spinning away from cornerbacks Terry Cousin and Brian Williams. Driver then was tackled by safety Sammy Knight and landed awkwardly.

Driver was helped off the field, then sat in the front seat of a motorized cart as he was taken to locker room at the two-minute warning to undergo medical tests. He did not return to the game.

After struggling early, Packers rookies James Jones and Brandon Jackson both showed bursts of their ability late in the second half. Jones caught three straight passes for first downs on the first drive under Rodgers, and the drive ended with two big plays by Jackson: an 11-yard catch to set up first-and-goal, and a 1-yard touchdown run on the next play.

And they'll have to keep it up if Driver doesn't return right away.

"Driver's a big playmaker for this football team," Jones said. "If it is something serious, everybody's going to have to step up. Hopefully, it's a little sprained ankle."

McCarthy said he second-guessed himself about not taking Driver out of the game at the same time he rested Favre.

"That's part of the game," McCarthy said. "It's unfortunate. Hopefully, it's not serious."

Game notes

Packers starting right guard Jason Spitz sustained a calf injury in the second quarter. ... Packers rookie linebacker Desmond Bishop delivered two separate hits that knocked the helmet off of Jaguars wide receiver Reggie Williams. And Jaguars tight end Jermaine Wiggins was shaken up after a big hit from rookie safety Aaron Rouse early in the third quarter.