Spiller's prognosis is much better than originally expected. (US Presswire)

If you saw the way C.J. Spiller rolled around on the field and walked off after injurying his shoulder Sunday, you probably feared the worst. The Bills likely did as well. But according to CBS Sports NFL Insider Jason La Canfora, the Bills are now much more optimistic, as they believe that Spiller's injury is a sprained AC joint and not a separated shoulder.

A source tells La Canfora the Bills expect Spiller to miss one-to-two weeks as a result of the injury.

The Bills lost starting running back Fred Jackson for several weeks to a knee injury. And when Jackson went down, Spiller stepped up, exploding through the first two weeks (and some of the third) to lead the league in rushing yardage.

It's possible Jackson could begin practicing as early as this week, but even if he doesn't, the Bills have third-string back Tashard Choice to step in. Choice looked good filling in for Spiller on Sunday.

For more NFL news, rumors and analysis, follow @EyeOnNFL on Twitter, subscribe to our RSS Feed watch Pro Football 360 daily at 3 p.m. ET and NFL newsletter. You can follow Will Brinson on Twitter here: @willbrinson.