It seems like the return of Willie Parker hinges on a variety of things. It seems like the Steelers were happy with his attitude and his (albeit limited) performance, but they seem unlikely to pay too high a price for an injury prone back-up, even in an uncapped year.
So what is the likelihood that he gets offered more money? Here's some notable names in the RB free agent pool. The big ones are Ronnie Brown, Pierre Thomas, and Darren Sproles. I think it likely that their respective teams keep them. The Charges would be insane not to resign Sproles, but if they don't Sproles will be the most desirable option at RB. There is also some rumors that the Chargers might look to trade LT or potentially even cut him. LT is older than FWP (and as injury prone) but he has a glitz about him that might make him more desirable.
Of the other free agents there are a few that project as starters (all are restricted FAs except for Chester Taylor):
Leon Washington (28) is the most intriguing, but he's coming off a brutal leg break and there is some questions about his size. With the emergence of Shonn Greene the Jets might pass on Washington, but with their passing game as it is, I see them trying to maintain their strength in the running game.
Jerome Harrison (27) seemed to be the more explosive back in CLE, but we're talking about the Browns here so who knows. I would expect them to hold on to Harrison, but he might draw some other offers.
For a more known commodity a team might try Le'Ron McClain (25), whose natural position is fullback, but who nearly had a 1,000 yd season when he filled in at RB. He might get an offer of RB money which means the Ravens would probably let him go since he doesn't figure into the ground game too often.
LenDale White looks like a bust so far, but he's still young (25) and someone might be willing to take him on.
Another unknown is the Falcon's Jerious Norwood (27) who has shown flashes greatness, but hasn't had the opportunity or health to put it together. He's similar to Parker in speed and size and at two years younger might bea better value.
Two third down options would be Mike Bell (27) and Chester Taylor (30). Bell was primarily used in garbage time and short yardage situations and Taylor was primarily used on passing downs. Both showed they still had gas in the take and would be excellent compliments somewhere. Sean Peyton has a crush on Bell and Taylor seems to fit into the Viking's plan so well I expect both to stay on their teams, but in an uncapped year some big spender might lure them away.
Younger untried options would be Kenneth Darby (27), Jason Snelling (26) and Kolby Smith (25). Of these Snelling has shown the most promise, but there was a contingent in St. Louis that wanted to trade Steven Jackson and rebuild with Darby as an adequate replacement. I would expect Parker to rank higher than these three, but the point is more about the options available to teams in finding a back-up RB. This is not to mention the up coming draft where the is no end to the supply of cheap available talent.
Looking at the names available Parker might find a smallish 1/2 year contract from the Steelers his best option. I have many fond memories of Parker breaking it to the outside and burning past the secondary and I think he should that he has enough left in the tank to be a contributor, the only question seems to be at what cost?