Landing defensive coordinator Mike Nolan arguably was the Falcons’ biggest offseason acquisition in 2012.

The former head coach and well-traveled defensive guru was expected to lift the unit out of the lower reaches of the NFL rankings and possibly turn them into a destructive and tenacious force to be reckoned with.

Things started well, as Nolan blended 3-4 principles with the Falcons’ base 4-3 alignments. He creatively used defensive end Kroy Biermann in a hybrid linebacker role that had him sometimes racing 25 yards down the field in coverage.

Safeties William Moore and Thomas DeCoud turned into marauding ballhawks and made their way to the Pro Bowl as alternates.

But while the defense played a key role in the Falcons’ 8-0 start, it showed signs of leakage down the stretch before collapsing in the playoffs — when they struggled in all areas: rushing the passer, stopping the run and pass coverage. They specifically had problems covering tight ends.

The defense finished last season ranked 24th in total yards, 25th in third-down efficiency and 27th in sacks-per-passing attempt. The numbers weren’t all bad, though, as the defense finished fifth in scoring (18.7) and tied for fifth in takeaways (plus 13).

The Falcons know their defense must improve in order to fulfill the team’s Super Bowl aspirations. So it was no surprise when they used six of their eight draft picks on defensive players and traded up twice to get targeted players.

“You get better when somebody either gets beat out or somebody raises their level of play,” said Nolan, who saw his unit match up against the offense for the first time this offseason in OTAs last week. “I would like to think that the guys that we drafted and hopefully a free agent or two that we didn’t draft, a college guy and then a guy like Osi (Umenyiora), would help us step up our game as well. You never really know.”

The Falcons went heavily on defensive backs in the draft, selecting two cornerbacks and two safeties. First-rounder Desmond Trufant is slated for the starting lineup at right cornerback, while second-rounder Robert Alford could land the nickel-back slot.

Safeties Zeke Motta and Kemal Ishmael could land roles in a ‘Big Nickel’ package to help slow some tight ends.

The linebacker corps of Sean Weatherspoon, Akeem Dent and Stephen Nicholas appears set to remain intact.

The first order of business is getting the pass rush rolling.

In addition to signing Umenyiora, the Falcons drafted Malliciah Goodman and Stansly Maponga in the fourth and fifth rounds. They also have Cliff Matthews and Jonathan Massaquoi competing for spots in the pass-rush rotation.

“We are teaching some different techniques in pass rush along with our scheme,” defensive line coach Ray Hamilton said. “That is an area that we have kind of personalized as a defensive line. That’s one of our targeted goals, to get better as a pass-rushing team, to affect the quarterback and hopefully get him on the ground some more.”

Stopping tight ends in the passing game will be key. The linebackers struggled in the regular season against New Orleans and in the playoffs against Seattle and San Francisco.

The Falcons may switch the scheme to include faster safeties in some of the packages of five and six defensive backs.

“We are all about matching up, and we’re going to win some and they’re going to win some,” linebacker coach Glenn Pires said.

Nolan wants the linebackers to improve in coverage.

“If the tight end catches the ball, it could be anyone from a safety to a linebacker,” Nolan said. “It could be either one. They both have to improve on that. I’d like to see us get better at the linebacker position in covering.”

The Falcons needed miracle finishes against Carolina and Seattle at the Georgia Dome or they would have been 1-4 against read-option teams last season. They’ll have five regular-season games against read-option offenses in 2013, against Carolina (twice), Washington, Seattle and San Francisco.

Nolan and the entire defensive staff recently went to Clemson to study the read-option attack.

“Our visit there, as well as talking to some other people, was very beneficial,” Nolan said. “I thought they were great there. I was very impressed with their staff. (They were) very accommodating, but that’s where you have to go to get the roots to what the offense brings. Naturally, Seattle and San Francisco aren’t going to tell us anything.”

The Falcons know that stopping the read-option is vital to posting their sixth consecutive winning season and returning to the playoffs for a third consecutive time.

“We’ve spent considerable time with it,” Nolan said.