Shortstop is the last infield position we have to look at it and it's without a doubt the most exciting position. If you look at Starlin Castro's fWAR you can't help but be impressed, but if you look at his rWAR he looks much less impressive. Whereas UZR sees Castro as a well below average fielder, Total Zone sees him as just plain terrible. His career rWAR is only 2.8 while his fWAR is double that.
For the projections I've been ignoring defense. I don't trust UZR and Total Zone well enough. While I'm certain Castro is at best a well below average fielder right now, I'm not at all certain how many runs below average he's been. I'm less certain either are all that useful in considering for 2012 projections. You can add or subtract based on what you think he's worth defensively.
The Dav-Marcel and Clay Davenport's Marcel projections. You may notice that I have a .350 wOBA for Steamer while Fangraphs has him at .337. I'm not entirely sure what the difference is. I've used the basic wOBA formula so I imagine that inflates the numbers I've posted above a little bit. If you estimate his wOBA based on the OBP and SLG you get .338. Steamer includes HBP and ROE projections, which I have included. That increases the wOBA. Most of the other projections don't include either one. I don't believe any of them include ROE, but Bill James I think includes HBP. When you have 9 projections it's not going to make much of a difference overall. If I drop the Steamer projection to match Fangraphs .337 I get an average projection of .333 rather than .334. No big deal.
If I estimate 650 plate apppearances and use a .325 league wOBA that makes Castro worth 3.1 offensive WAR next year. Darwin Barney would be the back-up to SS, but will hopefully play sparingly. Estimating Barney's projected value at SS over 50 or so plate appearances just isn't worth it.
2012 is Castro's final year making league minimum. The time to consider signing him to a long-term extension is getting closer. He'll have 4 years of arbitration eligibility. Using +.5 WAR improvement for someone Castro's age we get something like this over the next 5 years.
That's what we would estimate Castro to be paid over the next 5 seasons. Obviously you'd want a discount if you're going to take the risk of signing him to a long-term extension. Contracts longer than 3 years already get a 10% discount. That takes it down to just under $50 million. I figure the Cubs should pay no more than 70% of his projected value over the next 5 years if they were to sign him long-term. That's 5-years and $35 million.
That's the maximum I'd consider paying Castro at this point. I'd probably shoot for something closer to 5-years and $28 million. I might try to buy one or two more years too. The Cubs may want to wait awhile considering the potential legal issues surrounding Castro at the moment.