A team-by-team look at the most indispensable players (non-quarterbacks) in the division.

The NFL, perhaps more than any professional sport, is a league filled with replaceable players. By sheer numbers, fielding 22 players on offense and defense makes it difficult for a single cog to be above the team, especially for non-quarterbacks.

But there are several players vital to AFC North teams. Here are four difference-makers in the division:

Troy Polamalu helps take the Pittsburgh defense to another level when he's on the field. Chris Morris for ESPN.com

PITTSBURGH STEELERS: TROY POLAMALU

To define Polamalu's importance, look no further than last season. Pittsburgh missed the playoffs in 2009, mostly because its defense was unable to hold leads in the fourth quarter without its star safety in the lineup.

Polamalu missed 11 games with a left knee injury, and it appeared the other 10 defenders were overcompensating for Polamalu's absence by blowing routine assignments. Polamalu provides a calming influence, and his greatness can be measured by his teammates playing at a higher level when he's in the game.

Steelers defensive coordinator and 2010 Hall of Famer Dick LeBeau recently said he cannot find a weakness with Polamalu. He's athletic, smart, instinctive and excels against the pass and the run.

Pittsburgh's defense without Polamalu is good (No. 5 in 2009), but with Polamalu, it might be the best in the NFL.

CLEVELAND BROWNS: JOSH CRIBBS

Where would the Browns be without Cribbs?

For starters, you probably can erase two or three wins from last year's 5-11 record. Cribbs also might have saved Browns head coach Eric Mangini's job.

Cribbs was one of the few bright spots for Cleveland last season. He made the Pro Bowl as a kick returner, but his ability to run the Wildcat also added a new wrinkle to the Browns' struggling offense, which finished last in the NFL in 2009.

The Browns plan to expand Cribbs' role, both in the Wildcat and as a receiver. The more the team is able to get the ball in his hands, the better.

Despite Cleveland adding pieces in the draft and free agency, Cribbs remains the Browns' most-feared player. He's also a locker-room leader and, perhaps, the new face of Cleveland sports now that LeBron James signed with the Miami Heat.

BALTIMORE RAVENS: RAY LEWIS

Lewis, 35, is no longer the Ravens' best player. That distinction could be shared by Ray Rice, Ed Reed and Haloti Ngata. But Lewis' leadership still makes him Baltimore's most indispensable player.

Lewis remains the heart and soul of a team many feel is a Super Bowl contender this year. Physically, the Ravens are stacked with talent at nearly every position. But there's no one in the locker room who can replace Lewis' role as the motivational leader.

On the field, Lewis made his 11th Pro Bowl last season, recording 134 tackles and three sacks. Backups Dannell Ellerbe or Tavares Gooden would be significant drop-offs if Lewis were injured. On the other hand, the Ravens have plenty of quality replacements ready for Rice, Reed and Ngata. Even Joe Flacco has a capable backup in veteran quarterback Marc Bulger.

CINCINNATI BENGALS: CEDRIC BENSON

Cincinnati is a team better defined by the sum of its parts. But if I had to pick the most important non-quarterback, it would be Benson.

The Bengals have two very good cornerbacks: Leon Hall and Johnathan Joseph. They have plenty of receivers, including two who have put up Hall of Fame-caliber numbers in Chad Ochocinco and Terrell Owens. But Benson is the workhorse who makes it all work. Benson opens things up for the passing game, which was inconsistent last season, and he moves the chains to help keep the defense off the field.

Second-year tailback Bernard Scott will help Benson carry the load this year. He showed positive flashes as a rookie, but the former sixth-round pick remains unproven. With Cincinnati expected to pass more, Benson might not match his career-best 1,251 rushing yards from last season. But that doesn't make him any less important.