Using defensive metrics*:
In 2006, Bartlett saw his first 800+ inning season, and it resulted in a .863 RZR with 26 OOZ plays.863 RZR with 26 OOZ plays. In 2007, his playing time increased while his RZR lowered to .804, but he saw 67 OOZ plays. In 2008, Bartlett's RZR raised to .807, but only had 44 OOZ plays. Interestingly enough, Bartlett actually saw more balls in zone in 2006 (293) than 2008 (285) despite playing in more than 200 less innings, what does that mean? I'm not entirely sure, but it's irrelevant to Bartlett. In 2007, Sean Smith's TotalZone ratings had Bartlett worth six runs, this year Bartlett is worth -8 runs, Brendan Harris was rated at -9. The Fielding Bible had Bartlett +13 (plays) in 2006, +18 in 2007, and -1 in 2008.
Essentially every metric that had a crush on Bartlett prior to 2008 gave him the cold shoulder. That's bad, namely because those same metrics gave us hope that Bartlett was a defensive wizard, and while he looked good, he apparently was not as good as perceived. The problem for us, and the Rays, is deciding whether this is indicative of a true talent change or simply an anomaly. Smith uses the previous five years worth of data to project fielding runs, and while Bartlett projects modestly (0.9 wins), it's not quite as stunning as 2008's projection (1.3 wins). I don't expect Bartlett to be quite that good, instead likely in the 0.0 > x < 0.5 wins range.
Unfortunately, there's no BABIP-type red flags, or obvious fluke measures here. Bartlett did suffer a knee injury later in the year, and that very well could've limited his range. Only one thing is for sure: he wasn't nearly as good defensively in 2008 as he was in 2007 or 2006, and that's worth weighing, how much is to be determined.
*Yes, we all know the weaknesses of defensive metrics, but this isn't the post to debate their merits. What's more likely: the system suddenly didn't like Bartlett, or Bartlett had a down year?