On Tuesday, the Buffalo Bills placed rookie tight end Lee Smith on Injured Reserve, promoting Kevin Brock from the practice squad to fill his roster spot. Smith became Bills player No. 15 to land on IR this season - not a record by any means, but certainly a meaningful number.

Of those 15 players, a round dozen were expected to have a big impact on the team's success this season. Let's take a look at those dozen players - a list that includes the two best performers on the team.

Fred Jackson. Had the best season of his career, even if it only lasted parts of 10 games. Jackson was so good early this year that he had a legitimate case for league MVP consideration. A broken fibula ended his season, and as good as C.J. Spiller has been at times in his stead, Jackson is Buffalo's best player.

Marcus Easley. A heart condition derailed a promising pre-season and a lot of buzz about a player that many expected to emerge as the team's No. 2 receiver this season. Easley still has not played in an NFL regular season game.

Roscoe Parrish. The speedy slot receiver was expecting big things after a solid debut season with Chan Gailey, but caught just one pass for 16 yards before succumbing to a season-ending ankle injury.

Donald Jones. Though he struggled to fill in for Lee Evans as the team's No. 2 receiver, Jones has still been missed since exiting the lineup with an ankle injury. He may not have proven himself worthy of being a starter this season, but he's certainly a guy worth having around, and a good football player.

Lee Smith. Though he carried no pre-season expectations after being a late waiver claim, Smith emerged as a solid sub-package, blocking tight end behind Scott Chandler this season. His upside is limited, but he's a good football player, too.

Eric Wood. For the second time in three pro seasons, a nasty leg injury ended Wood's season prematurely - this time a shredded knee. Wood had been performing well in his new role as the full-time center, and the line has missed his leadership qualities since exiting the lineup.

Kyle Williams. Slowed all season by an Achilles injury, Williams landed on IR and has since had surgery to remove a bone spur that had been irritating the tendon. In losing Williams, the Bills lost their best defender, and far too much of the onus has fallen on Marcell Dareus' shoulders as a result.

Torell Troup. The Bills pumped up Troup's strength gains and progress as a player all summer, but a bad back prevented him from ever realizing that potential this season. Back injuries can be tricky, and Troup has had surgery to try to alleviate the problem in the hopes that he'll be fully healthy come 2012.

Shawne Merriman. Buddy Nix's self-appointed savior for the pass rush, Merriman looked like a shell of his former self before a pre-existing Achilles issue flared up on him and cut his season short. Even though he was only mediocre, he's been lightyears better than any other player at his position this season, and is clearly still the team's best and most respected pass rusher.

Chris White. Drafted to help re-build the core of the team's special teams units, White proved himself a highly valuable performer covering kicks early in the season. His presence has been missed in that capacity ever since he landed on iR.

Terrence McGee. The injury-prone veteran cornerback was injured on the first defensive play of the season, came back six weeks later, played five solid games, and then tore up his knee. He's played in 15 games in the past two seasons, and hasn't completed a full 16-game schedule since 2004.

Rian Lindell. Injured while trying to make a tackle on a kickoff return, Lindell's shoulder problem proved insurmountable. His replacement, Dave Rayner, has showed off a huge leg, but has also been highly unreliable kicking field goals. Lindell was 13-of-15 this season.