There’s a revolution going on this year in Florida this year and it’s happening in perhaps the most underrated aspect of baseball today. According to John Dewan’s Plus/Minus system from the Fielding Bible, the Florida Marlins and Tampa Bay (Devil) Rays were the worst two teams in baseball last season in team defense, clocking in at 88 and 107 plays below average respectively.

Using Tango’s figure of 0.8 runs per play, we come up with figures of 70 and 86 runs these defenses cost their teams’ bottom lines. Those are exceptionally damaging magnitudes. For reference, according to wOBA, Barry Bonds was worth a little over 60 runs over average back in both 2003 and in 2004. Moving their defense up to league average would be akin to removing a replacement level player from your lineup and inserting Barry Bonds from that era.

Fast forward to almost the end of 2008 and how are those teams doing now? Well, we don’t have final numbers from Dewan’s system just yet, but a similar plus/minus system, used by The Hardball Times, gives us some clues. They have the Rays at a positive 13 plays (10 runs) and the Marlins at just negative 16 plays (13 runs).

If those values hold through the end of the season, and assuming they generally reflect what Dewan’s system will report, that would represent an improvement of 57 runs for the Marlins and an astounding 96 runs for the Rays. You want a reason why the Rays have become the team they are this year? Well there’s several, but don’t you dare overlook defense. When a team can add 100 runs to it’s net runs scored – runs allowed total, that’s a huge swing in success’ direction.