Despite the defensive letdown in the NFC Wild Card playoffs, one factor that points to a promising future outlook for the Green Bay Packers' defense is that it achieved what it did in 2009 - ranking No. 1 in the league against the run and No. 2 in total yards allowed - with significant contributions from rookies.

As the season wound down, Clay Matthews and Brad Jones were the two starting outside linebackers, B.J. Raji was filling in at nose tackle for an injured Ryan Pickett, cornerback Brandon Underwood was pressed into duty in the dime package, and Jarius Wynn was getting some snaps as a reserve down lineman in nickel.

"We played a lot of young players," defensive coordinator Dom Capers said in an extended session with reporters after the season ended. "Hopefully the experience those guys gained will make them that much better.

"We're talking about five rookies there that contributed some."

Barring an even worse rash of injuries on the defensive side than the Packers endured this past season, it's hard to imagine needing so much help from newcomers as this defense grows and progresses.

At the same time, the upside for some of these players is considerable.

Matthews, a first-round draft pick, looks like a keeper at right outside linebacker, having led the team in sacks with 10 (plus another in the playoffs) and developing into a pass-rush threat that opposing offenses must game-plan against.

There was significant evidence of that in the season's last two games, when Matthews dominated en route to seven quarterback hits in the regular-season finale at Arizona and then one week later saw repeated chips, help and double-teams in the playoff rematch.

"We have to respond to that," Capers said. "You get one guy that starts to do the things that Clay's done the second half of the season, Clay's going to get a lot of attention. He will from now on.

"It ain't going to be a secret. Now when you play the Packers, they're going to have to find a way to block Clay Matthews coming off the edge."

There's no one penciled in to be that edge rusher on the other side just yet, because the future of unrestricted free agent Aaron Kampman is up in the air, and no one can be sure Jones is the long-term answer.

But the rookie seventh-round draft choice held his own in starting the final six regular-season games when Kampman was lost to a knee injury. Despite missing much of training camp with a back injury and then not making his debut from scrimmage in this defense until midseason, Jones finished tied for third on the team with four sacks and, though he didn't dominate against the run, he wasn't the liability at the point of attack some thought he might be at just 239 pounds.

"I thought for a guy his size he played fairly physical," Capers said. "You could tell he's not afraid to mix it up in there from a physical standpoint. We always felt he had a little innate pass rush to him. I think he's got enough athletic ability to drop into coverage. I think he did a good job for the first year.

"There's lot of things he can improve on, but there aren't many guys that come in and start that many games as a rookie. He probably surprised a lot of people."

Capers noted he had at least three opposing coaches come up to him during the second half of the season asking how the Packers found Jones in the seventh round of the draft. But for outside linebacker to be considered one of the prominent positions in a 3-4 scheme and for the Packers to succeed with two rookies there says something about the potential down the road.

"Clay's play speak for itself, and I think we have a really, really good young prospect there," Capers said. "The fact that Brad started all those games at the end of the year is encouraging. Two rookies, those guys are definitely going to get better. It's important to both of them. I like their approach, I think they're professional, and they sure understand now a lot more about what it takes than they did before the season started."

So does Raji, who no doubt wanted to make a bigger impact as a rookie (36 tackles, one sack) but had several obstacles working against him that hopefully won't be in his way in 2010.

Raji sustained a rather severe ankle injury in the final preseason game that sidelined him for the first two games and limited him somewhat for about the first half of the season. But even before that, missing the first two weeks of training camp in a contract dispute kept him out of many of the roughly 10 padded-practice installations of Capers' defense.

"He had absolutely the toughest start because of missing camp," Capers said. "As you go through training camp, you're giving each guy a packet about a quarter-inch thick (each day), and he got one two-and-a-half inches thick. There's absolutely no way you're going to comprehend everything in there, when somebody hands you a playbook of that size."

{sportsad300}In addition, Raji started out playing defensive end, added duties as an inside rusher in the nickel package, and eventually was playing for Pickett at the nose - his most natural position -down the stretch.

That didn't give him the opportunity to master any one spot, but the varied experience should help him as soon as next season.

"We asked a lot of B.J.," Capers said. "Most of the time you get a rookie in and you say, 'Let's put the rookie in one position and let him learn that technique.' Well, he had to learn a whole bunch of techniques because he was playing end, then he was playing nose, and he was playing inside in sub. He handled all of it and he was playing his best football at the end of the season."

The other two rookies on defense, Wynn and Underwood, weren't asked to do nearly as much, but their development in their second seasons will be watched closely.

Aside from special teams, Wynn got most of his snaps as an inside rusher in nickel or other sub packages, and his quickness and long arms make him potentially a good fit for that role. The Packers played sub defenses probably more than 50 percent of the time this past season, so a team's rotation of pass rushers can never be too deep.

The same can be said at cornerback, where Underwood moved into the dime role after Pat Lee, Will Blackmon and Al Harris all went on injured reserve with knee injuries, and Underwood recovered from a hip problem of his own.

Like Jones, Underwood didn't see any snaps from scrimmage on defense until roughly midseason. That lack of experience made it difficult to counter Arizona's spread formations in the playoff game, but the playing time he did get should help him as he's sure to be in the thick of the battle for spots on the depth chart at cornerback, assuming the three injured corners return healthy and ready to go next season.

"In this day and age, you can't ever have enough cover people," Capers said. "Like what we went through this year, all of a sudden Pat Lee and Will Blackmon and Al Harris, those guys go down, you start facing teams that are going to put four wide receivers out there on the field. You have to match people up on them."