If their plan works, the Washington Redskins soon will have a defense that resembles the Pittsburgh Steelers’ successful 3-4 scheme, the model for what Coach Mike Shanahan hopes to achieve.

For now, though, the Redskins probably should focus on emulating the Green Bay Packers, who have fared better than Washington in the transition from the 4-3. Green Bay acquired two outstanding players at the scheme’s most important positions – nose tackle B.J. Raji and outside linebacker Clay Matthews – before committing to the change in 2009. The Redskins struggled this season, in large part because they lacked the right personnel, according to two NFC assistant coaches and one AFC assistant who studied video of Washington.

After their worst defensive performance since 1954, the Redskins must make major personnel changes – especially along the line – if they hope to improve next season. The 2011 free-agent class could be the best in league history (if the NFL’s labor conflict doesn’t affect it), and Washington has financial flexibility. The Redskins also hold the 10th overall pick in the upcoming draft.

It seems unlikely that the Redskins could address all of their needs on defense this offseason, but they should get started, because there’s a lot of work to do.

“What we did this year as a defense . . . it wasn’t acceptable at all,” said cornerback and defensive co-captain DeAngelo Hall, who was recently selected to his third Pro Bowl.

“A lot of it comes down to having the right guys, the right people, in the right places, and I think that’s what this year was about for Coach Shanahan and Haz (defensive coordinator Jim Haslett). They saw what they needed to see, and there’s probably gonna be a lot of changes, cause this definitely wasn’t good enough.”

For most of the season, the Redskins ranked last in the league in defense and finished 31st out of 32 teams.

They gave up an average of 389.3 yards per game, were 31st against the pass (261.7) and 26th against the run (127.6). Opponents averaged 23.6 points against Washington – tied for 21st. Washington did produce 10 more turnovers (27) than last season, which was among its goals, but still had a minus-four turnover differential.

, the difference between takeaways by the defense and giveaways by the offense.

The 2010 defense was the third-worst in franchise history, measured by yards relinquished. Only the 1954 and 1949 squads were more porous.

In its first season in the 3-4, Green Bay ranked second in the league in total defense, and was No. 1 against the run and first with 40 turnovers and a differential of plus-24. Despite losing many key players to injuries this season, the Packers were fifth in yards given up, second to the Steelers in points per game at 15.0 and tied for second with 47 sacks.

With their two first-round picks in the 2009 draft, the Packers selected Raji ninth overall from Boston College and Matthews 26th overall from Southern California. They have provided the foundation for Green Bay’s success in the scheme, which works best with a dominant nose tackle occupying multiple blockers in the middle and outstanding edge rushers at linebacker.

In “this defense, you need a big guy sitting in the middle, which B.J. gives you, and you need a guy that can rush and drop off the edge and impact games,” Packers defensive coordinator Dom Capers said recently. “Both of those guys, you’ve seen their play constantly get better since they’ve been here.”

Obviously, Raji and Matthews are not solely responsible for the Packers’ success, said the three NFL assistant coaches, who requested anonymity to speak freely. They have many talented teammates, including five-time all-pro cornerback Charles Woodson, a probable Hall of Famer. But Raji and Matthews set the tone up front.

Second-year Redskins linebacker Brian Orakpo is a strong pass rusher, but he is not as skilled in coverage as Matthews is, or as talented overall as the two-time Pro Bowler, who finished fourth in the league with 13½ sacks, the coaches said. And the Redskins do not have anyone who compares favorably with Raji, a Pro Bowl alternate.

The Redskins had planned for Albert Haynesworth to play nose tackle, but that effort failed spectacularly. They also hoped that Maake Kemoeatu would fill the spot after missing the entire 2009 season because of an Achilles’ tendon injury, but Kemoeatu rarely displayed his pre-injury form.

Without a consistent force in the middle, and with starting defensive ends Kedric Golston and Adam Carriker not among the NFC’s elite players at their positions, the Redskins were often ineffective along the line, the coaches said. Washington focused on offense in the 2010 draft, choosing only one defensive player, linebacker Perry Riley (fourth round, 103rd overall).

Shanahan selected left tackle Trent Williams with the No. 4 overall pick, considered a wise move because the previous regime had neglected the offensive line for years. Many free agents who normally would have been unrestricted during the previous offseason were restricted under the terms of the uncapped 2010 season, so the Redskins had fewer options to help improve their defense.

Faced with clear personnel deficiencies, Shanahan nonetheless moved forward with the switch to a 3-4 instead of delaying. Needing an outside linebacker to play opposite Orakpo, they moved end Andre Carter, who struggled in his only previous season as a linebacker in the NFL. Versatile backup Lorenzo Alexander, primarily a defensive lineman and special-teams standout in his first four seasons with Washington, supplanted Carter as a starter in Week 4.

But Alexander does not have the speed or skills to stand up and rush the passer or drop in coverage, as required in the 3-4, the assistant coaches said, so the Redskins lacked balance at outside linebacker. Orakpo led Washington with 8½ sacks. Alexander had 1½ and the Redskins finished tied for 25th with 29 sacks.

Washington’s poor performance in the 3-4 came after the team spent most of the decade among the league’s top defenses. From the 2000 season through the 2009 season, the Redskins had a top-10 defense eight times. Washington ranked lower than 10th only in 2003 and 2006 (25th and 31st, respectively).

Shanahan made the switch because “the 3-4 has been the best defense in the NFL over a period of time, and Coach Shanahan came here to win,” Alexander said. “But it’s a process. And we’re in the process now.”

In fairness to the Redskins, the Packers “still probably aren’t quite where we want to be, I know we aren’t,” Capers said. “It changes as you go along. You know what you want it to look like, but you aren’t just going to snap your fingers and have it look like that overnight.”

For the Redskins, bolstering the line would be a good place to start.

Washington must get better up front, the assistant coaches all said. Golston is listed at 6 foot 4 and 310 pounds, and Kemoeatu (6-5, 350) and Carriker (6-6, 315) also are large men. But they would not be front-line players for the Steelers or Packers.

The Redskins’ defensive line simply did not make enough plays.

“They do all the dirty work,” one of the NFC assistants said of defensive lines in the 3-4. “They eat up space, but they also gotta be playmakers. They gotta get to the ball and make plays. They’re not gonna get a lot of sacks . . . but they need to be big-body types that can move.”

Golston, who is scheduled to undergo hernia surgery, is likely to be a free agent. Kemoeatu is under contract for $1.5 million in 2011 and Carriker is signed for $1.42 million. Backup nose tackle Anthony Bryant, who showed promise while starting the final three games, has a base salary of $640,000 in 2011.

At linebacker, the Redskins need another strong pass rusher to complement Orakpo, the coaches said. And Orakpo, who will be paid $480,000 next season, must continue to improve in coverage.

Alexander, under contract for $650,000, is better suited for a backup role, especially with his significant responsibilities on special teams. The team is not expected to pay Carter’s $4.075 million option bonus, which would make him a free agent.

Ageless inside linebacker London Fletcher has a $4.9 million base salary in 2011 and is considered a key part of Shanahan’s long-term plan, according to people familiar with the situation. Inside linebacker Rocky McIntosh, also likely to be a free agent, missed valuable study time during the previous offseason while protesting his contract situation, and is not expected to return.

In the defensive backfield, the Redskins must replace free safety Kareem Moore, who played on a bad knee for much of the season and is “more of a backup,” the other NFC assistant said. Moore will be paid $555,000 next season. Cornerback Carlos Rogers could leave in free agency.

Strong safety LaRon Landry, who had the best season of his career, is signed for $3.715 million. Hall will receive $4.5 million.

Even if Washington drafts a quarterback in the first round, it has second- and fifth-round picks, and two each in the sixth and seventh rounds that could be used to help the defense. Haynesworth was suspended without pay for the remainder of the season Dec. 7 for conduct detrimental to the club, but Shanahan apparently still believes he can trade the two-time all-pro for another draft pick, according to team employees. Regardless, the Redskins no longer are counting on their most talented defensive player.

In addition to whatever moves are made, the Redskins should experience some degree of improvement next season because “we’ve set the foundation of the defense,” Fletcher said. “We understand the scheme, the basic principles of it. Now it’s just making it go from elementary, to middle school to high school. But it takes time.”

It seems apparent that Shanahan, who inherited a player-personnel mess, is building toward the 2012 season, the coaches surmised. That would be his third season in control, and by then he could have the roster shaped, for the most part, the way he wants it. But the key, the assistants said, is getting the defensive front seven set.

“Personally, I think that I know what we need to do to get better,” Haslett said recently. But can you get all the pieces you think you need?”

Staff writer Barry Svrluga contributed to this report.