FLOWERY BRANCH, Ga. -- The Atlanta Falcons have a big hole to fill on the defensive line after first-round pick Peria Jerry sustained a season-ending knee injury in a victory over the Carolina Panthers.

The rookie defensive tackle tore up his left knee in the fourth quarter of Sunday's 28-20 victory, which improved the Falcons to 2-0 for only the seventh time in the team's 44-year history. He was placed on injured reserve Monday.

"It's very unfortunate for Peria," coach Mike Smith said. "It's a very, very violent game on the offensive and defensive lines. We're going to miss him, but we've go to move forward."

The Falcons already were thin along the defensive front, so the loss of Jerry is especially damaging. Johnson will move up to start alongside Jonathan Babineaux, and seventh-round pick Vance Walker was signed off the practice squad. Atlanta also has Trey Lewis, who missed all of 2008 with a knee injury and has yet to play this season.

Johnson played two games for the Dallas Cowboys in 2005 and 11 games for Houston the following year, including three starts. He failed to make the Texans in 2007 and was cut by the New York Jets during the preseason last year before finally earning a spot with the Falcons.

"I guess their scouts were paying attention and kind of found me," Johnson said.

Now, he's a starter for a team coming off a trip to the playoffs and hoping for even bigger things this season.

"It's tremendous," Johnson said. "All I can do is smile when I think about it."

No matter who starts, the Falcons figure to do plenty of shuffling on the interior line, depending on the situation. Chauncey Davis has been used mostly at end, but he can move inside to provide the sort of quickness Jerry provided in passing situations.

"Anytime you lose somebody to an injury, it's very tough," Davis said. "But we just have to deal with it and keep moving on. Some other guys are going to have to step up and play a big part in our defense."

Perry has struggled with durability in both college and during his brief career with the Falcons. At Mississippi, he missed four games as a freshman because of an ankle injury, underwent offseason foot surgery after appearing in eight games as a sophomore, and he missed the 2008 season opener after arthroscopic surgery on his right knee.

Since being selected 24th overall by the Falcons, Jerry missed time during a May minicamp because of sprained right knee. He also left the season-opening victory over Miami with a chest injury before going down with the most serious problem yet.

Jerry had not made much of an impact on the stat sheet -- one assisted tackle and one quarterback hit in Atlanta's first two games -- but the Falcons expected him to play a more prominent role as the season went along.

"Anytime you lose a player - especially a first-round pick and a guy who's the starter -- it's something you have to address," Smith said. "But one man's misfortune is another man's opportunity."