Updated

They are the heart and soul of a defense, asked to be difference makers on a weekly basis.

Whether it is stuffing ball carriers, dropping back in coverage or setting their sights on the quarterback and creating mayhem in backfields, linebackers are called upon to do a myriad of things to help their team win.

Here are the top linebackers heading into the 2013 season:

OUTSIDE LINEBACKERS:

ANTHONY BARR (UCLA): Certain to be an intriguing story line come the 2014 NFL Draft, this once rarely used fullback got a new lease on his football life when he moved to the defensive side of the ball last year. Jim Mora Jr. made the right call in reconstructing Barr because the 6-foot-4, 245-pounder is now regarded as the best player at his position heading into this season thanks to some gaudy stats in 2012. In 14 starts, Barr racked up 83 total tackles, leading the Bruins in both tackles for loss (21.5) and sacks (13.5), en route to All-America second-team honors and the All-Pac-12 first team. He could have left the college ranks for the NFL after last year, but may actually improve his already inflated draft stock with another dominant campaign.

KYLE VAN NOY (BYU): This Cougar continues to get better and better, culminating in last year's All-America campaign. The 6-3, 245-pound Van Noy was named a Third-Team All-American, finishing 2012 with 53 total tackles, 22 tackles for loss, 13 sacks and six forced fumbles. He put an exclamation point on his season with a remarkable performance against San Diego State in the Poinsettia Bowl, collecting 3.5 tackles for loss, 1.5 sacks, one interception, one fumble recovery, one blocked kick and two touchdowns. BYU has a real force on the defensive side of the ball in Van Noy, who can obviously do it all.

C.J. MOSLEY (Alabama): There aren't many lists of the top college defenders that doesn't include one or more Alabama player. The main reason the Crimson Tide have dominated the FBS ranks has been a monster defense and Mosley has been as responsible as any for the team's back-to-back national titles. The 6-2, 235-pounder was a consensus First-Team All-American in 2012, an All-SEC first-team selection and a finalist for the Butkus Award, leading Alabama with 107 total tackles, eight tackles for loss, four sacks and two interceptions. Mosey will fit right into the NFL with his skills in passing situations, as he excels in coverage and as a playmaker off the edge.

RYAN SHAZIER (Ohio State): He may not have the ideal size for the next level, but there is nothing small about the way this Buckeye plays. The 6-2, 222- pound Shazier stood out on a very good defense, leading Ohio State in tackles (115) and the Big Ten in tackles for loss (17), en route to All-Big Ten first- team honors, as well as some All-America accolades. He was the first sophomore to eclipse the century mark in tackles since James Laurinaitis (2006) and posted six games with 10 or more stops in 2012. He has the speed and natural instincts that scouts drool over. If he can put a few more pounds on his frame, Shazier just may be the complete package come draft time.

KHALIL MACK (Buffalo): This may be a case of a big fish in a small pond. In just two seasons in the Mid-American Conference, the 6-3, 244-pound Mack has dominated like no other. He already ranks fifth in school history with 34 tackles for loss and is tied for the school record in forced fumbles with seven. As a sophomore last year, Mack earned All-MAC first-team honors, finishing with 94 total tackles, 21 tackles for loss and eight sacks. He will once again fail to generate the kind of excitement that others on this list will simply because of where he plays, but Mack's continued production will not go unnoticed by the NFL.

HONORABLE MENTION: Adrian Hubbard (Alabama), Christian Jones (Florida State), Prince Shembo (Notre Dame).

INSIDE LINEBACKERS:

A.J. JOHNSON (Tennessee): In an SEC that has plenty of defensive playmakers, the 6-3, 243-pound Johnson led the league in stops per game (11.5), finishing his sophomore season with 138 total tackles (fourth-most in the country). A starter at middle linebacker the last two seasons, Johnson earned All-SEC second-team honors in 2012, after being tabbed a consensus Freshman All- American in 2011. The scary thing about Johnson is that he continues to get bigger and stronger, while having a real feel for the game. A power player at the point of attack, he finishes plays emphatically. Whether he remains in Knoxville past this season remains to be seen, but his NFL star is shining bright heading into his junior campaign.

ERIC KENDRICKS (UCLA): The Bruins may have the best linebacking duo in the country in the aforementioned Barr and Eric Kendricks. The 6-foot, 230-pound Kendricks was often overshadowed by Barr's exploits last year, but in reality it was more of a symbiotic relationship. Just a sophomore in 2012, Kendricks led the Pac-12 in tackles and his 150 total stops were the most by a Bruin since 1978. While he will once again fail to match the hype surrounding Barr, Kendricks is equally as important to UCLA and its quest for a third straight Pac-12 title game appearance.

ANDREW JACKSON (Western Kentucky): After recording a sophomore season that included 109 total tackles and 17 tackles for loss, the 6-1, 265-pound Jackson did not have the luxury of flying under the radar in 2012 as a junior. That didn't matter, though, as Jackson actually improved on those numbers, posting 122 stops, 17.5 tackles for loss, two sacks and four forced fumbles, picking up All-Sun Belt first-team honors for the season straight season. He is a bit on the short side, but that hasn't kept Jackson from seeking out ball carriers and taking them down. He won't get the publicity he deserves playing for the Hilltoppers, but that won't matter in his final season at WKU.

MAX BULLOUGH (Michigan State): A picture of consistency, the 6-3, 242-pound Bullough has started 27 straight games for the Spartans and will begin his third season as the team's middle linebacker. Like a fine wine, Bullough gets better and better with age. As a junior last season, he was tabbed an All-Big Ten first-team member, leading the team with a career-high 111 total tackles, 12.5 tackles for loss and two sacks. A north-south defender, Bullough is at his best inside, with ideal size and power.

SHANE SKOV (Stanford): It has taken some time for the 6-3, 245-pound Skov to get back on track following a knee injury that cost him most of the 2011 season, but Stanford's defense is star-studded and the fifth-year senior fits right in. He didn't play in the season opener for the Cardinal last year, but started the next 13 games, leading the team in tackles (81), with nine tackles for loss and 2.5 sacks. He didn't really trust the knee early on, but as his confidence grew, so did his production. A perfect fit for what Stanford does on defense, Skov could put any lingering questions about his health to rest with a superior final season on the Farm.

HONROABLE MENTION: Trey DePriest (Alabama), Avery Williamson (Kentucky), Chris Borland (Wisconsin).