Now it's time to flip the script.
Here's a look at five clubs around the league that are promising to do things differently on defense in 2013:
New Orleans Saints
Sean Payton spent last season in exile watching his New Orleans Saints allow more yardage than any team in history. He vowed to change that and hired Rob Ryan as defensive coordinator to install his beloved 3-4.
It sounds good on paper, but a successful move away from the 4-3 starts with longtime defensive end Will Smith making noise at outside linebacker and Martez Wilson growing as a pass rusher.
The back of this defense was a disaster last season, but the signing of free-agent cornerback Keenan Lewis and the drafting of safety Kenny Vaccaro should help the Saints improve on the 293 passing yards they allowed per outing one season ago. Honestly, it can't get much worse.
The Wide-9 has gone the way of the carrier pigeon in Philadelphia, where all signs point to a three-man front for the Eagles. New defensive coordinator Bill Davis has been given freedom to mold this unit to his liking, but he's preaching patience.
"This year is absolutely the hardest transition year we're going to have," Davis told the Philadelphia Inquirer.
Kelly -- surprise, surprise -- wants "versatility," and Davis emphasized he'll build a "multiple" unit. Expect to see more blitzes than under Juan Castillo.
The Inquirer this week called former end Trent Cole a "fish out of water" at outside linebacker, but Davis promised Cole and Brandon Graham are making progress. In the secondary, it's a long-overdue fresh start without Nnamdi Asomugha and Dominique Rodgers-Cromartie to kick around.
Top 100 Players of 2013
It's less about scheme and more about identity in Jacksonville. New coach Gus Bradley cut his teeth in Seattle, where the Seahawks thrived on a multiple-front defense that used long, hyper-physical defensive backs to shut down opponents. Jacksonville plans to follow suit.
Bradley is fashioning a 4-3/3-4 hybrid attack and hinted this week that end Jason Babin fits in well as a right-side-rushing Leo chess piece. "He has a lot of the traits that we're looking for," Bradley said.
The biggest change is in the secondary, where the Jaguars drafted no fewer than five defensive backs. Jacksonville was a mess against the pass last season, but rookie safety John Cyprien and first-year cornerback Dwayne Gratz will help make this a more punishing group. There's reason for hope.
The Browns have promised to attack on offense, and Ray Horton's defense boasts a similar philosophy.
After two years in the 4-3, Cleveland is shifting back to the 3-4. Success boils down to the play of pass rusher Paul Kruger and defensive end Desmond Bryant, both of whom were handed a mountain of money in free agency to make Horton's scheme click. First-round pick Barkevious Mingo will play outside 'backer opposite Kruger and gives the Browns a potential X factor up front.
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Monte Kiffin's 4-3 is coming to town, meaning DeMarcus Ware and Anthony Spencer will move from outside linebacker to end. Cowboys fans shouldn't lose any sleep over Ware. He's a dominating seeker of quarterbacks, and he will continue to generate chaos with his hand in the dirt. Spencer is less of a lock to see equal production.
It widely was assumed Kiffin would lean on his beloved Cover-2, but cornerback Morris Claiborne said Dallas will "play a lot of man-to-man" and build its weekly game plan to fit the roster.
That's far from surprising. All these defenses have a preferred core alignment, but the trend in today's NFL is scheme flexibility. Adapt or vanish.