Back in September, we broke down the Buffalo Bills' 53-man roster, position-by-position. Now that the Bills' season has ended, we'll review those grades:

Position: Running back (preseason grades)

SNAP COUNTS

Fred Jackson -- 57.1 percent

C.J. Spiller -- 33.5 percent

Frank Summers -- 19.4 percent

Tashard Choice -- 9.1 percent

Evan Rodriguez -- 1.6 percent

Ronnie Wingo -- 0.3 percent

DEPTH

Preseason take: When looking at some of the other top rushers around the league -- Adrian Peterson, Doug Martin, and Arian Foster -- none have a player of Jackson's caliber as a second option. The one knock against this unit would be its lack of another young player to develop. The Bills had Kendall Gaskins (rookie) and Zach Brown (first-year) in training camp, but neither stood out. Choice, whose contract expires after this season, is an upgrade-able piece. Grade: A-

Postseason review: Back in the preseason, many expected Spiller to overtake Jackson as the "lead" back in the offense, especially after comments from offensive coordinator Nate Hackett. Ultimately, it was Jackson who was the top dog. Still, the point remains the same: few teams have the one-two punch that the Bills have at running back, so this grade was accurate. In the end, Choice was upgradeable: the Bills waived him in early December. In terms of young players, Ronnie Wingo fits the bill but saw just four snaps this season. His future remains uncertain.

RELIABILITY

Preseason take: The biggest concern for the Bills lies with Spiller. If he becomes the "featured" back in the Bills' offense, as he is expected to be, can he hold up over the full season? Spiller will need to prove he is durable, even when taking 250 or more carries in a season. Likewise, Jackson is 32 years old and hasn't played a full season since 2010. Losing either would put some stress on the other. Grade: B-

Postseason review: Spiller did not prove he was durable. After taking more snaps than Jackson in the first two games, Spiller suffered a quad/knee injury in Week 3 and then an ankle injury in Week 4. He was never the same. He still finished the season with 202 carries, which was just shy of his career high. Meanwhile, Jackson played a full season, which was remarkable given a nagging knee injury, and later, a rib injury. Combined, Spiller and Jackson missed just one game, so this grade should have been higher.