Friday, February 6, 2009

Update: Ben Sheets, Durability, and Why The BE Player Rating System Values It So Much

February 6, 2009 - Well, it surely didn't take too long. Even before he could sign a contract, Ben Sheets has been put back on the shelf with an injury that looks like it could prevent Sheets from playing this season. And that brings us to the topic of the day. Why is durability important in shelling out a baseball contract and why should Major League general managers think of it more often, or highly, when they do?

Now any player can get injured. It's a physical game, not up to the level of football or hockey, perhaps, but baseball is still a physical game. But some players get injured more often. And some players get injured enough that they don't play full seasons, even though the injuries are not up to the level of costing them season long trips to the injured reserve list. And that's why some statistics, really popular ones by sabermetrics fans today such as OPS and OPS+ can't be used as a guru to value, at least without considering whether that value was attached to durability.

The PEVA player rating stat developed by baseballevalution.com uses durability as a highly measured factor. In fact, one-third of the entire player rating is based on use, durabilty to us. How do we measure durability or use and do we forgive a player who gets injured once? We measure durability by grading each player on a scale between the maximum and average values of two categories. For a pitcher, the first category is Games or Games Started, giving precedent in the factor to Games Started; the second category is Innings Pitched. For a batter, the categories are Games Played and Plate Appearances. These two factors provide a girth to the PEVA Player Grade and helps make it solid. We think that's important. The remainder of the factors that go into making the Player Rating comb the more sexy stuff for stat geeks; yes, ... OBP and SLG (OPS for your folks, although we count it even more highly than adding the two together), Run Production, etc.

It matters, folks, whether a player is on the field, because, in simple terms, he can't help his team win if he's sitting the pine, for whatever reason. And you certainly don't want to give him a contract that could harm your club down the line if his history tells you there's a good probability he won't give you innings or at bats. But yes, because the Player Rating system had at its core mission to mirror the way real baseball values its player, using Player Salaries as its constant, we do forgive some injuries in a way. We do this by using two averages of the past several seasons, by reaching back to years when injuries didn't come into play. But we do not forgive the injury in a single season by discounting that it happened; and that's what we're seeing in baseball contracts given out recently, albeit not in the case of Ben Sheets because the injury came up before he could sign the dotted line.

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