Well, if you have a ton of roster space, I suppose you can keep those guys around. Still, I'm thinking there's about zero chance Rivers will be needed this year. McCown...maybe, if you are using Warner. Henry...maybe if you have Brown.
There's a fairly good chance that these guys will be a waste of space that you can substitute sleepers with. Even if these guys are needed, the chances that another team is going to want these guys is pretty low. I don't know how your waiver system works, but if these guys are FA's, I'm sure you could be able to get them if an injury does occur.
I think I would rather stash reserve players that fit these criteria:
a) Guys that could end up starting near the end of the year due to an NFL team's playoff standing. Indianapolis, Seattle, and Denver backup players might be good pickups. Examples would be Dominic Rhodes, Mack Strong (I think Maurice Morris is out for the year, but I might be wrong - I assume he'd be the backup), or even Ron Dayne (if Denver runs away with the division).
b) Sleeper players on teams that have easy matchups near the end of the year. St. Louis, Seattle, and Jacksonville probably have the easiest schedules left. So, guys like Matt Jones, Shaun McDonald (yeah, a stretch), and Jerramy Stevens (if he's not taken already) might be worth looking at.
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