EAST RUTHERFORD, NJ - OCTOBER 20: David Harris #52 of the New York Jets reacts during the second quarter against the New York Jets at MetLife Stadium on October 20, 2013 in East Rutherford, New Jersey. (Photo by Maddie Meyer/Getty Images) David Harris. (Maddie Meyer/Getty Images)

By Dan Durkin–

(CBS) When assessing the Bears’ linebacker play in 2014, it’s hard to find many positives. Injuries played a part in the collective struggle, forcing nine different starting combinations onto the field over the course of the season. However, the lack of quality depth and slow development of younger players were the root causes.

When discussing the vulnerabilities of defenses, conversations hone in on deficiencies along the front seven or the back seven. What’s the commonality among both? The linebackers.

In switching to a 3-4 base defense, the Bears will carry a greater number of linebackers on the roster than they have in the past.

As it stands, they have six linebackers on the roster currently: Jon Bostic, Shea McClellin, Christian Jones, Khaseem Greene, DeDe Lattimore and Jonathan Brown, who was signed to a future/reserves contract. The coaching staff is now in the process of determining which defensive ends can potentially fill the critical outside linebacker roles in Vic Fangio’s scheme, evaluating players like Lamarr Houston, Jared Allen, Willie Young, David Bass and Cornelius Washington.

However, the inside linebackers also play a crucial role in Fangio’s scheme. The “Mike” linebacker in Fangio’s scheme lines up to the strong side of the offensive formation, while the “Jack” linebacker lines up to the weak side of the offensive formation. The profiles are somewhat interchangeable, and the differences lie in the responsibilities of each, as the Jack is more involved in pass coverage.

At the NFL Scouting Combine, Bears coach John Fox said that McClellin will be looked at both on the inside and outside. Some have theorized that McClellin’s issues have been rooted in him playing in the wrong scheme all along. Given McClellin’s performance on the field, it’s difficult to believe that playing out of position is the primary driver for his struggles. He simply lacks functional strength to stack and shed blockers.

Jones played three positions in a 3-4 at Florida State — defensive end, outside rush linebacker and inside linebacker. He could be a viable candidate for the Jack linebacker position, but taking inventory of the group, the Bears need to up the talent and competition at both inside linebacker spots this offseason.

Here are some free agent options who may pique the Bears’ interest in free agency.

David Harris (6-foot-2, 250 pounds, 31, nine-year veteran)

A Jets’ 2007 second-round draft pick, Harris has spent the majority of his career manning the inside for Rex Ryan’s attacking 3-4 defense. Once Ryan took over in 2009, Harris started 96 straight regular-season games, and he’s registered at least 99 tackles in six of his eight NFL seasons.

Harris played the Mike linebacker role in Ryan’s defense, setting the front for one of the league’s more exotic schemes. Harris isn’t a flashy player, rather a reliable force who’s assignment sound and consistently in the right place at the right time. He’s also an effective A-gap blitzer who has 30 career sacks.

Harris will be highly sought after on the free agent market and will certainly draw interest from Buffalo, which Ryan now coaches and whom just traded linebacker Kiko Alonso. Harris will be among the highest-paid free agent inside linebackers, likely signing a deal with an average annual value of $6 million-$8 million.

Sean Weatherspoon (6-foot-2, 244 pounds, 27, six-year veteran)

A Falcons’ first-round draft pick in 2010, Weatherspoon missed the entire 2014 season with an Achilles’ injury and half of the 2013 season with a Lisfranc injury. Health issues aside, Weatherspoon is a highly athletic player with exceptional lateral quickness.

Weatherspoon is a “chase in space” player capable of tracking the ball-carrier from sideline to sideline, then quickly attacking downhill. He wins with footwork in space to get in position to make plays, but he has a tendency to miss open-field tackles by going for a knockout blow instead of wrapping up. If he can harness his ability to break down at the ball-carrier and wrap up, he will greatly improve his efficiency as a run stopper.

Clearly, Weatherspoon’s injury history is a concern. However, he’s a fast and physical linebacker, capable of playing multiple spots. And at 27, he still has productive football ahead. He will draw heavy interest on the open market and likely sign a deal with an average annual value of $4 million-$6 million.

Bruce Carter (6-foot-2, 240 pounds, 27, five-year veteran)

A Cowboys’ second-round draft pick in 2011, Carter is an elite athlete who has contributed against the run and pass; he’s just been plagued by inconsistency. Carter has experience both as an inside linebacker in a 3-4 defense and on the weak side in a 4-3 defense. His position and assignment versatility makes him an intriguing option for teams with needs at the second level.

Last season, Carter led all linebackers with five interceptions, showcasing the ability to get proper depth in a zone drop, read a quarterback’s eyes and ultimately make a play on the ball. He’s yet to play a full season but has 32 career starts. Carter could be an ideal fit as a Jack linebacker in Fangio’s scheme given his athleticism and ability to mirror tight ends up the seam.

Carter’s raw ability and scheme versatility to play in both a 30- or 40-front will drive up his stock on the open market. He will likely sign a deal with an average annual value of $3 million-$5 million.

Nate Irving (6-foot-1, 245 pounds, 26, five-year veteran)

A Broncos’ third-round draft pick in 2011, Irving underachieved for the first three seasons of his career but started to come into his own last year when thrust into a starting role for Denver. Unfortunately for Irving, he suffered a partial MCL tear that cost him the second half of his season.

Prior to the injury, Irving was on pace to have his best year as a pro. He’s a powerful player against the run who projects as a Mike linebacker in Fangio’s scheme. Prior to earning his way into the starting lineup, Irving was a solid, core special teams contributor for the Broncos.

Irving’s medical evaluation will be a crucial as he makes the rounds as a free agent. Combining the knee injury with questions about his coverage skills and ability to be a three-down linebacker, Irving could be a free-agent value. He will likely sign a deal with an annual average value of $2 million-$3 million.

Dan Durkin covers the Bears for CBSChicago.com and is a frequent contributor to 670 The Score. Follow him on Twitter at @djdurkin.