FLOWERY BRANCH, Ga. (AP) -- Losing linebacker Sean Weatherspoon to a season-ending injury has caused a ripple effect throughout Atlanta's defense.
Weatherspoon, a first-round draft pick in 2009, would've started on the inside and run the huddle, but his torn Achilles tendon means that Paul Worrilow and Joplo Bartu now hold starting jobs at both inside spots as the Falcons transition to more 3-4 fronts.
''Yeah, we had to do all of the (offseason training activities) without Sean,'' Worrilow said Wednesday on the second day of mini-camp. ''It's kind of the same roles we had last year, but now heading into training camp, we're going to have to pick up our leadership.
''Being vocal out there is what you need at this position.''
Rookies Prince Shembo, Marquis Spruill and Yawin Smallwood are in the mix to earn snaps behind Worrilow and Bartu, who moved into starting roles last year as undrafted rookie free agents.
It gives the Falcons, who went 4-12 last season, plenty of inexperience on the inside of a defense that ranked last in third-down efficiency and second-worst against the run and had the third fewest sacks.
Atlanta has played without Weatherspoon for much of his career. The former Missouri standout set career highs with 80 tackles, four sacks, 14 tackles for losses and eight pass deflections in 2011, but that was the only season that he played 16 games.
Weatherspoon's injuries last season were magnified by the ineffectiveness of Stephen Nicholas and Akeem Dent, each of whom failed to hold significant roles and gave Worrilow and Bartu a chance to play.
The season ended with Worrilow and Bartu playing the first- and second-most snaps on the defense, but coach Smith hesitates to say that both have secured starting jobs.
He wants to see how much Shembo, Spruill and Smallwood can push them.
''My big point to our guys from the very beginning is it's all going to be about competition,'' Smith said. ''We're going to compete and to me that's the most important thing and the thing that's the most fun about the game of football and any athletic endeavor is going out to compete.''
It's not an ideal situation for Smith and defensive coordinator Mike Nolan, but without lots of veteran depth, the Falcons have no other alternatives.
''Gosh, we've got some really young LBs,'' Smith said. ''We drafted three and I think their head is swimming. We've probably got them on overload right now. You can see their athleticism. They can make plays but then there are those that you go, 'What in the world was he thinking?' "
Career defensive ends Osi Umenyiora, Kroy Biermann, Jonathan Massaquoi and Stansly Maponga are lining up at outside linebacker, but Nolan says the Falcons aren't too worried about their long-time veterans adjusting to new roles.
''There is a lot of youth,'' Nolan said. ''As I've experienced in the past, you'd like to have that youth in about three or four years rather than always being (raw) youth because that's when they're at their best.''
The linebackers have been studying film of other successful 3-4 fronts in the league.
For Massaquoi, there's plenty to learn, particularly in watching how well outside linebackers such as Tamba Hali of Kansas City, Robert Mathis of Indianapolis, Ahmad Brooks of San Francisco, Terrell Suggs of Baltimore and Jason Worilds of Pittsburgh man their positions.
''It's always good to look at guys from those teams that have perfected that position,'' Massaquoi said. ''For me, it's all about being out here and getting the reps and getting thrown in the fire.''
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