FLOWERY BRANCH, Ga. -- Falcons fans may have an especially hard time figuring out who's playing linebacker Monday night when Atlanta hosts the New York Jets.
Opening day starting linebackers Akeem Dent and Sean Weatherspoon will not play. Versatile linemen Kroy Biermann, who the Falcons also used in pass coverage like a linebacker, has a torn Achilles tendon and is out for the season.
Who will man the spots is a bit of a mystery.
Undrafted rookie Joplo Bartu is expected to make his third pro start. Omar Gaither appears likely to fill in for Dent (foot) in the middle just three weeks after signing with Atlanta. The other outside spot could come down to how sound undrafted rookie Paul Worrilow's left knee is.
If his left knee is not deemed sound, then perhaps Stephen Nicholas will re-claim the starting spot he lost heading into the season, re-gained two weeks ago because of Weatherspoon's sprained foot and then lost again last week to Worrilow.
"As you know in this league, it's a `Next-man-step-up-and-make-plays,' mentality," said Nicholas, who led the Falcons with 116 combined tackles and assists in 2012. "I anticipate playing every week. In this league, you never know. I can see playing more."
Falcons head coach Mike Smith said that defensive coordinator Mike Nolan and linebackers coach Glenn Pires have been "burning the midnight oil," trying to bring newcomers Gaither and Jamar Chaney up to speed. They signed Sept. 17.
"We have to determine with the group of linebackers what they're capable of doing," Smith added. Some of them did not "go through our offseason program so that puts them at a disadvantage. It's not an excuse; it's just a fact."
Gaither was practically offended when asked if his defensive coordinator was simplifying the game plan because the Falcons have several new and young players.
That includes rooking starting cornerback Desmond Trufant, second-year defensive end Jonathan Massaquoi and the linebackers.
This isn't the first time Gaither's had to ramp up quickly. He signed with the Raiders in the middle of last November, played in the last seven games and started four.
"I'm fortunate that I've been in the NFL for eight years . . . so the only thing you really have to do is learn the vernacular. You just really need to find out what they call it," he said. "Also, you're learning game plans instead of an entire system. You pick up on the system doing that. You're doing it backwards, really, learning enough to play the game.
"I would hate for them to (simplify it), actually. It's my responsibility to learn it and play well. I think that's one of the reasons they signed me, because I've done it in the past."
Nolan's defensive gameplan will probably be somewhere in the middle, not as sophisticated as if all three starters were playing, but not high school-level, either.
"We're going to be dealing with crowd noise, which will make it a bit more complicated, but we also have some new pieces who haven't been with us as long as other guys," Smith said. "We're going to have to make sure that we have a package that fits our least denominator, and by that I mean the guy who's been around the least amount of time."
Don't look for Bartu to make excuses.
Undrafted out of Texas State, he said the Falcons were the only NFL team that offered him a chance to try out. Bartu believes in himself and Atlanta's defense.
"We learned most of this in (the spring). For me, (Nolan's) not simplifying anything," he said. "Every game your confidence gets better. If I wasn't confident, I wouldn't be here."
Notes: Middle linebacker Akeem Dent (foot) and left tackle Sam Baker (knee, ankle) did not practice Friday, and have been ruled out. Cornerback Asante Samuel (thigh) and linebacker Paul Worrilow (knee) returned to limited participation. Wide receivers Roddy White (ankle) and Julio Jones (knee) were also somewhat limited. Running back Stephen Jackson (hamstring) worked out on the field without a helmet, and did not participate in practice.