The Chicago Bears will have a number of their returning front seven defenders switching positions as they move towards a 30 front as their base defense for the 2015 season. They will still have a weak-side outside linebacker (Will) and a strong-side outside linebacker (Sam), but their responsibilities differ slightly from the previous 4-3 defense in Chicago. The Will is the premier pass rusher in the 3-4 defense with the Sam having edge setting responsibilities.

The two inside linebackers in new Chicago defensive coordinator Vic Fangio's 3-4 defense are called the Mike and the Jack. When I spoke with the fellas over at Niners Nation, our sister site that covers the San Francisco 49ers, they explained to me that Fangio's Mike is more of the downhill run plugger and often lines up on the strong side of the formation. The Jack will often line up on the weak (or open) side of the formation and have more coverage responsibilities.

Another thing to keep in mind about Fangio's linebackers, we may see them lining up in various places along the line of scrimmage. His ILBs may rush from the edge or run stunts, his OLBs may slide inside and attack the interior of an offense. Expect multiple looks in 2015 from the Bears.

The three down lineman aren't always working with a 2 gap principle. On occasion, Fangio will have just one or two of his linemen playing 2 gap. Other times, all three will be shooting single gaps. It all depends on the game situation and the personnel he has on the field.

And speaking of the personnel...

General manager Ryan Pace added an edge rushing OLB in Pernell McPhee and head coach John Fox announced that last year's big free agent prize, defensive end Lamarr Houston, would move to outside linebacker.

I would expect both McPhee and Houston to line up all over the formation, but each would start out as OLBs in the base D. Also expected to be outside linebackers are former defensive ends Jared Allen and Willie Young.

Defensive ends David Bass and Cornelius Washington are two others that may fit best at 3-4 OLBs in the new scheme, but we've yet to hear a definitive word on either. Since both are bottom of the depth chart guys, we'll probably need to wait until they 'get on the grass' (to borrow a John Fox phrase) to find out their position. My early guess is that Bass transitions to OLB and Washington sticks at DE.

EDIT: Chicago Bears sign LB Sam Acho

Acho has four years of experience playing as a 3-4 OLB in Arizona. He has started 32 of the 51 games he has appeared in and he can play either the right or left side.

Once the Bears begin practicing, it's possible that either Allen or Young will end up back at defensive end, but for now the outside linebacking corps looks like this. (And for the record, I'm on the draft Vic Beasley bandwagon)

OUTSIDE LINEBACKERS

Pernel McPhee

Lamarr Houston

Sam Acho

Jared Allen

Willie Young

David Bass

Earlier this week the Bears signed Mason Foster to play inside linebacker, with my guess being his skill set is a fit for the Mike position. Returning linebacker Jon Bostic has started 17 games in his two year Bears' career (appearing in 29 overall) with the bulk of his playing time spent in the middle. Thirteen of Bostic's career starts were as a 4-3 Mike and at 6'1", 246 pounds, inside linebacker is his best position in a 3-4. My guess is he starts out at the Jack ILB spot.

Yesterday John Fox mentioned that former first round draft pick Shea McClellin would begin the 2015 season as an inside linebacker. Here's some of what Fox said about McClellin,

"It hasn't gone as well for him as far as position fit. In fairness to him, that's not to be judgmental on anybody else, but I think the transition is we're going to start him inside because it's a harder position to learn as far as run fits and how they set in there. But he'll be both."

Another player that figures to be in the mix inside is Christian Jones, but I believe he's another player that will learn both ILB and OLB eventually.

Khaseem Greene (6'1", 241) and DeDe Lattimore (6'1", 237) are two other holdovers that will possibly compete inside. Jonathan Brown (6'1", 230)) doesn't have the athleticism to play anywhere but the Mike in Fangio's 3-4 scheme, so he probably stays there in Chicago. Of these three, I think Lattimore has the most upside.

Here's how I see inside linebacker shaping up so far.

INSIDE LINEBACKERS

Mason Foster

Jon Bostic

Shea McClellin

Christian Jones

DeDe Lattimore

Khaseem Greene

Jonathan Brown

The Bears finally signed a couple of legit 3-4 defensive ends on Tuesday. Both Jarvis Jenkins and Ray McDonald are well versed in a 30 front and both can play in a 2 gap scheme.

Unfortunately these are the only two DEs on the roster that I have any faith in. We talked about Washington possibly staying on the d-line, but he's still a project. Austen Lane is on the roster, but he didn't play last year and he only had 30 snaps in 2013 while a member of the Detroit Lions.

Jamil Merrell (6'4", 252) is a reserve/futures guy that was signed when the Bears were still a 4-3 team. Some scouts thought he'd be a fit as a 3-4 OLB, but I'm just not sure he's athletic enough to make the switch. He'll be another guy that has his fate determined once he hits the grass.

The wildcard at defensive end is Will Sutton. I personally feel he doesn't have the length to play DE in a 3-4, but according to the Bear Report's Aaron Leming, the Bears view Sutton at defensive end. Perhaps he'll come in on sub packages and rush the passer. Sutton (6', 310) thrived as a one gap player as a junior at Arizona State, but he's another guy we'll have to wait and see perform at training camp.

Here are the DEs currently on the roster.

DEFENSIVE ENDS

Jarvis Jenkins

Ray McDonald

Austin Lane

Jamil Merrell

Will Sutton

The Bears do have two players that fit the mold of a 3-4 nose tackle on the roster. Jeremiah Ratliff made 4 Pro Bowls as a 1 gap penetrating NT in Dallas, so he understands the position, and at 6'4" he has the length to slide down the line on occasion too.

Second year pro Ego Ferguson could back up the nose, but he did play some DE in college. I wouldn't be surprised to see him get reps up and down the line as well. Brandon Dunn will be there competing for a job.

Here are the interior defensive linemen on Chicago's roster so far, plus expect Will Sutton to get some reps in there too.

NOSE TACKLES

Jeremiah Ratliff

Ego Ferguson

Brandon Dunn

That about sums up the front 7, but what about the back end of Chicago's defense?

I talked to the Niners Nation guys about what kind of coverage Vic Fangio likes to run and they told me he uses a lot of combination coverage. We should expect to see a lot of off man and zone with pattern matching, and some two deep man to man.

If you want a real good Xs&Os read on the pattern matching coverage Fangio uses, I stumbled across this article.

They also informed me that Fangio rarely blitzed during his time in San Francisco. But just because he doesn't blitz much, that doesn't mean he won't disguise which players are coming. That's part of the beauty of the 3-4 defense. You can usually expect 4 defenders to come on passing situations, but which 4 is the question offenses will have to answer.

The Bears did add some much needed talent and experience to their safety position, in 32 year old 3 time Pro Bowler Antrel Rolle. He's the first no-doubt-about-it starting safety the Bears have had in a while. He'll probably pair up with Ryan Mundy, unless the Bears make another move either in free agency or the draft, and Mundy and Rolle have experience playing together in New York.

Brock Vereen may get a look at nickel, but until we hear definite word from the coaches, he's still on the safety depth chart. Anthony Walters is more a special teamer.

Here are the current safeties on the roster.

SAFETY

Antrele Rolle

Ryan Mundy

Brock Vereen

Anthony Walters

John Fox hasn't spoken glowingly about many of his defenders, but he is high on cornerback Kyle Fuller. Fangio and defensive backs coach Ed Donatell got a good look at Fuller when both were coaching for the Niners last season. Fuller racked up 6 tackles and 2 interceptions in Chicago's week 2 win in San Francisco.

The other starting corner, Tim Jennings, was set to play inside as the nickelback when the season started and that is a possibility again this year. But that depends if the Bears can find another starting quality corner. Right now they don't really have one.

EDIT: The Bears have signed CB Alan Ball to a one year contract.

Ball has started 23 straight games for the Jags over the last two seasons, so I would expect him to be in the mix for one of the top 3 corner spots in Chicago.

EDIT: The Chicago Bears have re-signed cornerback Sherrick McManis

McManis has been a very good special teamer during his three years as a Bear, although he hasn't seen much playing time on defense.

Demontre Hurst was the nickel last year and he was adequate. Al Louis-Jean has good size to play outside, but he's still a raw prospect. Terrance Mitchell is in the mix for some depth.

Here's how corner looks so far.

CORNERBACK

Kyle Fuller

Tim Jennings

Alan Ball

Demontre Hurst

Sherrick McManis

Al Louis-Jean

Terrance Mitchell

What are your early thoughts on Chicago's defensive depth chart and what other positions do you feel the Bears need to address?