The Dallas Cowboys have missed the playoffs the past three seasons. Their big defensive change will help end that drought.

The offense, where coach Jason Garrett and quarterback and Tony Romo are the central figures, has faced heat for the team finishing .500 or worse from 2010 to 2012. But it's no secret that the slide has also been tied to not having former head coach Wade Phillips to influence the other side of the ball.

While Phillips, with his 3-4 savvy, has turned the Houston Texans' defense into an elite unit over the past two seasons, the Cowboys have been scrambling for answers. Their futile search culminated in the failed two-year experiment of Rob Ryan's attack version of the 3-4 scheme.

The decision in 2013 to bring in another venerable coordinatorâ€”Monte Kiffin, mastermind of the 4-3 Tampa 2 schemeâ€”to go in a new direction will be a solution. Unlike the several other teams undergoing radical front-seven shifts this season, the Cowboys already have the personnel to make it work well.

The biggest issue for the Cowboys has been pass defense. The yardage numbers will tell you they have improved from No. 26 in 2010 to No. 23 in 2011 to No. 19 last season. But under Ryan's aggressive mode, two things stood out: They gave up a lot of big pass plays without making enough of them.

They were burned before and after the catch, and when the Cowboys blitzed, opponents had a 101.5 passer rating last season. Dallas countered with seven interceptions, which tied for the league low, and an uncharacteristically low 34 sacks, in 2012.

The base concept of Kiffin's defense is zone, but it includes well-timed wrinkles with blitzing up front combined with some man coverage on the back end. With what Kiffin inherits on the outside and inside, the good news is that Dallas will maximize the fundamentals and raise the playmaking quotient.

Of all the teams switching fronts, no team is better and more established on the edge with its pair of outside linebackers-turned-ends.

"You would expect that DeMarcus Ware and Anthony Spencer will handle the move to end well," says former Cowboys offensive lineman Brian Baldinger, an analyst for NFL Netwrok.

Given that Ware (6-4, 254) can do just about everything, that Spencer (6-3, 250) is a late-blooming 2012 Pro Bowler who has evolved into a complete player on the other side, and that neither will have coverage responsibilities like in the past, they are set up to surge as pass rushers.

Ware and Spencer, who combined for 22 1/2 sacks in 2012, will put Kiffin in a position where heâ€™ll often be comfortable rushing just four and dropping back seven. Defensive tackle Jay Ratliff also has a history of pass-rush production to complement that cause well.

One AFC scout thinks there's another reason the Cowboys will thrive with their new look: The delayed returns they will receive on the cornerbacks they added in '12â€”veteran Brandon Carr and first-round pick Morris Claiborne.

Carr has the good size (6-0, 210) needed to excel in Kiffin's coverage scheme and is well versed in the Tampa 2 after playing his rookie season under Herman Edwards in Kansas City. His strength in run support is another key factor.

The Cowboys drafted Claiborne sixth overall because of his potential to make big plays on the ball. At a solid 5-11, 188 pounds, he is versatile enough to interchange between zone and man. Claiborne is ready to make an impact in Year 2.

Kiffin's scheme also requires a rangy, fly-to-the-ball middle linebacker, and Sean Lee offers just that. Two years ago, as an inside linebacker in Ryanâ€™s 3-4, he broke out with 104 tackles and was exceptional in coverage (four interceptions). He was on the verge of a monster 2012 before suffering a season-ending toe injury in the Cowboysâ€™ sixth game.

Justin Durant is one of Lee's new teammates, slated to start on the outside next to him. In just a short time with the team, Durant has seen just how driven Lee is to be the best.

"He's pretty intense, one of the most intense guys I've played with," Durant said. "He wants to know everything when he's out there."

Durant is coming off a good two-season stint in the Detroit Lions' version of the Tampa 2. After respecting Kiffin from afar, he's now seeing firsthand how the 73-year-old relates so well to much younger players and puts them in the right position to succeedâ€”much like Phillips did.

"We were in a bit of different situation when I came to the Lions in '11 and we went to the playoffs, but there's some of that same feeling with this team," Durant said.

With Romo and his many weapons in the passing game, the Cowboys already fit the profile of an NFC playoff team. But they needed to clean up their pass defense mess to balance that out, and that's exactly what will happen in 2013.

Stuck in transition

While the Cowboys are built to make a smooth 4-3 move under Kiffin, five teams going the other wayâ€”from a base 4-3 to a 3-4â€”face more significant hurdles in the transition to a new alignment.

Saints. Ryan was hired to bring back some of the aggressiveness that worked during the Saintsâ€™ Super Bowl season in Gregg Williams' better days.

Although the Saints have made major upgrades to clean up their back end with veteran cornerback Keenan Lewis and first-round safety Kenny Vaccaro, the front seven that was tailored to play in Steve Spagnuolo's one-and-done 4-3 zone-oriented scheme didn't get a personnel boost. The concern will be how they get a consistent edge pass rush from the still-green group of Cameron Jordan, Junior Galette and Martez Wilson.

Bills. They also are moving on from a short coordinator stint, as Dave Wannstedtâ€™s 4-3 system didn't work. Now the Bills are going back to a hybrid version of the 3-4 with former Jets defensive coordinator Mike Pettine.

It means yet another switch for Mario Williams, as he's gone back and forth from end to outside linebacker over the past three seasons with Houston and Buffalo. "You're not quite sure where he's most effective anymore," an AFC scout said. The Bills got a healthy and productive first season from Williams as a 4-3 end, and youâ€™d think they would cater better to their most talented defender.

Browns. They know they have added a well-rounded 3-4 outside linebacker, former Raven Paul Kruger, to anchor Ray Hortonâ€™s defense. And have already seen just how good inside linebacker D'Qwell Jackson can be in that attack scheme during the Brownsâ€™ days under Ryan. But it will be difficult for first-round outside linebacker Barkevious Mingo to be more than a situational player opposite Kruger, and there are questions about whether talented end Jabaal Sheard can handle the transition to outside linebacker.

Eagles. There's a reason they had to go out and get six new startersâ€”nose tackle Isaac Sopoaga, outside linebacker Connor Barwin, cornerbacks Bradley Fletcher and Cary Williams and safeties Kenny Phillips and Patrick Chungâ€”for the 3-4. Though they needed to go wholesale in the secondary regardless of their front, Sopoaga and Barwin were scheme-specific players needed to fill voids up front.

Former ends Trent Cole and Brandon Graham were much better suited to the Eagles' long-time 4-3 rush concepts, and talented second-year lineman Fletcher Cox had no choice but to move to 3-4 end instead of playing the nose. Inside linebacker DeMeco Ryans also has had a longer, more effective history as a 4-3 middle man, from his early Texans days to a strong first season in Philadelphia. The Eagles will need to put in a lot of time and hard work this offseason for their new personnel to jell and their holdovers to find their stride.