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Eric Seidman at Fangraphs has a nice article summarizing research on when sample sizes become (somewhat) reliable for hitters. The research suggests that the following stats begin to stabilize with the corresponding number of plate appearances: 50 PA: Swing % 100 PA: Contact Rate 150 PA: Strikeout Rate, Line Drive Rate, Pitches/PA 200 PA: Walk Rate, Groundball Rate, GB/FB 250 PA: Flyball Rate 300 PA: Home Run Rate, HR/FB 500 PA: OBP, SLG, OPS, 1B Rate, Popup Rate 550 PA: ISO Did not stabilize by 650 PA (the cutoff): BA, BABIP The underlying work was done by a well respected analyst who goes by the handle Pizza Cutter at the Statistically Speaking blog. His research on pitchers is here.

FanGraphs will be updating UZR every Sunday. Since we now definitely have enough of sample to get at each player's defensive skill, we can project that over a full year using UZR/150. DDJ: +12.9 Billy Butler: +62.0 Alex Gordon: +13.6 Mike Jacobs: +5.9 Alberto Callaspo: +11.9 Mark Teahen (RF): -0.3 Coco Crisp: -7.1 Mark Teahen (2B): -27.6 Mike Aviles: -18.1 Jose Guillen: -92.0 Willie Bloomquist: -148.4