Adam Reynolds asked in the comments what a potential Neil Walker extension might look like, so here's a stab at it.
The Pirates can pay Walker at the league minimum in 2012, and then he'll be eligible for arbitration for four seasons after that, assuming the Super Two rules don't change. There are a bunch of potential problems figuring out how much his contract should be worth:
1) He's not terribly young, and I wouldn't say he's loaded with upside. It wouldn't be a shock, obviously, if he had a power breakout and suddenly became, say, early-career Dan Uggla, but with slightly fewer homers and more line drives. But I don't know if that's terribly likely.
2) He's a liability on defense. This isn't really Walker's fault, of course, since he didn't play second in the minors, and he has improved this year. But the problem is that if he takes a step backward in a few years and has to move, he might not be an above-average hitter at his new position anymore.
3) Just in general, you don't see a lot of long-term deals for players in their pre-arbitration years for players who aren't better than Walker. (This was true for Jose Tabata also.)
There's no reason for the Pirates to go nuts with a Walker extension. He has a lot of value to them as a player with local ties, but he doesn't have that value with any other team, so there's no reason for the Pirates to overpay for any free agent years. And since he's under team control for five more years, and he is (again) not young, I don't really see any reason for the Pirates to buy out any free agent years anyway.
Walker was worth two wins above replacement in 2010 and has been worth 2.2 wins above replacement in 2011. Rickie Weeks was widely regarded as a frustrating player early in his career, but he was worth six wins above replacement in 2007 and 2008 combined, then made only $2.45 million in his first year of arbitration eligibility in 2009. Howie Kendrick was 1.8 wins above replacement in 2009 and got $1.75 million in his first year of arbitration eligibility. He then got $3.3 million in his second year after posting 1.8 wins above replacement.
So let's say Walker would make about $2 million in his first year of arbitration of eligibility. Assuming a normal pattern of salary escalation in arbitration, that would put his salaries at something like this. Keep in mind that I'm just spitballing here, although I looked at rising arbitration-year salaries of a bunch of players to confirm that these numbers roughly made sense.
2013: $2 million
2014: $3.3 million
2015: $5 million
2016: $7 million
TOTAL: $17.75 million
Now, keep in mind that if the Pirates were to go year-to-year with Walker, these salaries would not be guaranteed. So he should be willing to take a fairly substantial discount on these prices in exchange for financial security, particularly given that he won't be making much more than the league minimum until 2013 unless he gets a contract. Also, I suspect Walker will be motivated to work out a deal, given his local connections.
A good template for this deal might be the four-year deal Aaron Hill signed before the 2008 season. Hill posted 3.5 wins above replacement in 2007. He had one pre-arbitration year left before signing the contract, just like Walker does. He signed for four years and $12 million, plus three club options. That was a few years ago, but Walker isn't as good as Hill was.
Let's assume the Pirates want to sign Walker for five years, without buying out any free agent years. (Of course, the Pirates could opt to sign Walker to a shorter or longer deal.) They may wish to tack on an option at the end, but again, Walker isn't the sort of player you lock up in order to buy out his free agent years. He'll be 31 by the time the end of the 2016 season rolls around, and will probably be on the downside of his career. You lock him up to get him at a discount, and to provide cost certainty. So I think a five-year deal (and by a five-year deal, I mean a deal that begins in 2012) could look something like this:
Signing bonus: $1 million
2013: $1.5 million
2014: $2.5 million
2015: $3.5 million
2016: $5 million
... And let's say the Pirates would get an $8 million option for 2017.
That's five years, $14.25 million. I wouldn't be willing to go much higher than that.