Who do you guys think should win it? Bias aside, its a tie between Matthews and Harrison for me. Both players are irreplaceable to their respective teams, and both will be playing for the Super Bowl. 

From nfl.com 

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James Harrison, OLB, Pittsburgh Steelers

Harrison was an all-around force on Pittsburgh's vaunted second-ranked defense. For just the second time in his career, he tallied 100 total tackles, which included 10.5 sacks -- his third-straight year in double digits. Harrison also proved big in takeaways, coming up with two interceptions and forcing six fumbles, which was tied for second in the NFL.

Clay Matthews, OLB, Green Bay Packers

Matthews began the season with a fury, posting three sacks in each of the first two games, and never relented. Overall, the second-year pass rusher was fourth in the NFL with 13.5 sacks and had one interception -- that was returned 62 yards for a touchdown -- to lead a defense that finished fifth in yards allowed. He also forced two fumbles

Troy Polamalu, SS, Pittsburgh Steelers

After missing 11 games in 2009, Polamalu was back to his old ways this season. He was vital to Pittsburgh's defense finishing No. 2 overall. In 14 games, Polamalu tied a career high with seven interceptions, including one returned for a touchdown. He also had a sack and forced one fumble, which was critical to a Week 13 win over the Ravens.

Cameron Wake, OLB, Miami Dolphins

A two-time winner of the Canadian Football League's top defensive player award, Wake came into his own in just his second NFL season. He started all 16 games -- after starting just once in 2009 -- to turn into one of the league's top pass rushers. Wake finished third in the NFL with 14 sacks, posted three multi-sack performances and forced three fumbles