“I think in the big picture of things, I think we’ve done a good job in a lot of areas,” says defensive coordinator Jim Haslett. (John McDonnell/THE WASHINGTON POST)

If the Redskins’ first year under defensive coordinator Jim Haslett was about teaching a new philosophy and Year 2 was about finding the right pieces for the scheme, Washington’s third season running a 3-4 base defense will focus on perfecting a system that has produced mixed results so far.

The defense made noticeable gains in its second season, but coaches and players say they can make similar strides in the future. “I think in the big picture of things, I think we’ve done a good job in a lot of areas,” Haslett said. “We still can get better in a lot of areas. We can get stable in a lot of areas.”

A defense ranked 31st in the league in 2010 heads into the season finale this weekend with the NFL’s 13th-best unit, one that allows an average of 336.5 yards per game — a 53-yard improvement over last season. The Redskins have allowed 22.2 points per game (14th in the NFL) this season, also better than 2010, when Washington was ranked No. 21 and allowed 23.6 points an outing.

During the last offseason, the Redskins focused on giving Haslett the parts he needed to properly run his scheme. They chose defensive players with their first two draft picks, and four of their biggest free agent signings were defenders.

While Haslett says the team is no longer trying to force 4-3 pegs into a 3-4 holes, the scheme has been far from perfect. The Redskins produced 27 turnovers in 2010 but only 19 this season; they are ranked No. 24 in the NFL.

There are some major questions the team must address this offseason — none bigger than re-signing linebacker London Fletcher and making a decision on safety LaRon Landry. But coaches like the infusion of youth and believe the defensive unit is pointed in the right direction.

“You watch a couple teams that do run this type of scheme [and] you see they play fast,” Haslett said. They make up for a lot of things because they know where they’re going and what they’re doing and they’ve been together for a while and they just fly around. That’s where we’ve got to get to.”

The right pieces

In his 14th season, Fletcher doesn’t look — or play — his age. He entered the final week of the season with 18 more tackles than any other NFL player.

“I guess a lot more people get caught up in my age than I do,” Fletcher said. “At the end of the day, I’m going to be judged the same way these 20-something-year olds are gonna be judged.”

Fletcher will be an unrestricted free agent after the season. Though he’ll be 37 when the 2012 season begins, both he and Redskins coaches have said they want him to remain in Washington.

“From my perspective, I think he’s the perfect guy to help to keep building this defense,” Haslett said. “He’s got a lot of time left in him.”

The Redskins began Mike Shanahan’s first season as head coach with the oldest roster in the NFL. Since then, he’s been able to strike a better age balance on defense. DeJon Gomes is a rookie starting at safety, and Ryan Kerrigan is a rookie starting at linebacker. Second-year linebacker Perry Riley replaced veteran Rocky McIntosh at midseason. Coaches think defensive linemen Stephen Bowen and Barry Cofield have plenty of good years ahead of them.

The Redskins chose not to draft a quarterback last spring, instead selecting Kerrigan with the 16th overall pick. He quickly established himself as one of the team’s best playmakers. Through 15 games, Kerrigan leads the team with 71 / 2 sacks and nine tackles for a loss. Though he had to learn a new position, moving from defensive end at Purdue, he is the only Redskin to have played every snap on defense.

Washington then selected defensive end Jarvis Jenkins with the 41st pick. Jenkins has spent the entire season on injured reserve with a torn ACL, but coaches say his rehabilitation has gone well and he should be ready to participate in offseason workouts in the spring. Despite missing an entire season, he could be in line to start next fall.

Solid front seven

Whether it’s Green Bay, Pittsburgh or any other NFL team that runs the 3-4, coaches say the key to the scheme is finding the right bodies up front who can allow the linebackers and defensive backs to make big plays. After toiling with a rag-tag group in 2010, the Redskins feel they put together a front seven that can contribute into 2012 and beyond.

“You got a front seven that can be there for a long time,” Haslett said, “because they’re a bunch of young guys. . . . The front defensive linemen, there’s nobody over 27 or 26.”

Bowen and Cofield have long-term contracts. Defensive end Adam Carriker is coming off the best season of his career, and though he’ll be a free agent, he could be brought back. “He made a big jump from a year ago,” Shanahan said.

If the team re-signs Fletcher, it will have the same group of starting linebackers for a second straight season. Coaches expect Kerrigan and Riley to play more fluidly next year, and they’ll try to get more production out of Brian Orakpo, who has struggled at times with double teams and has seen some of his numbers dip in his third season. Though he’s improved in pass coverage, Orakpo enters the team’s final game with only seven sacks after posting 11 in 2009 as a rookie.

“I think we’ve taken some tremendous steps. . . . We got to be more consistent,” Orakpo said. “I think from Year 1 to Year 2, we hear it around the whole league — coaches, players — we’re a very top defense in this league.”

Coaches expect to see improvement across the board next season. And they say it wasn’t only front-line players who progressed in 2011.

“Not only do we have some first-teamers there, but we believe we have some second- and third-teamers there,” Shanahan said. “And that’s what you’re looking for is depth in that front seven, front eight. . . . We’re trying to keep all those players because that’s what we needed.”

Secondary help needed

When Shanahan announced in early December that Landry would finish a second straight season on injured reserve, he made no attempt to predict what the future might hold for the once-promising strong safety. “I really don’t know,” he said.

Landry’s Achilles’ injury forced him to miss 15 of the Redskins’ past 23 games. He’ll likely have surgery and will enter free agency needing to prove that he can again be a dominant player. Landry could look to sign a one-year contract in Washington or elsewhere, assuming the Achilles’ heals, to set the stage for a long term deal.

The secondary is the Redskins’ biggest defensive problem. Free safety Oshiomogho Atogwe battled injuries and was only able to start eight games in his first season in Washington. Cornerback Josh Wilson took a long time to adjust to the Redskins’ system and DeAngelo Hall gave up as many big plays as he made.

Coaches know there’s room for growth, but the Redskins feel they made big steps in this season.

“I think we still have a long way to go,” Haslett said. “We can improve in a lot of ways. There’s a lot of things we can do better, little things that make us a lot better in the long run.”