In today’s Prospectus Hit and Run piece, I revisit an early-season look at the Rangers’ improvement in Defensive Efficiency (the rate at which a team’s defense turns batted balls into outs), itself a follow-up of sorts to the record-setting improvement pulled off by last year’s Rays. They’re no threat to break that record, but they’ve done pretty well for themselves:

Team        2009   2008     +/- 
Reds        .705   .673    .032
Rangers     .701   .670    .031
Mariners    .712   .682    .030
Dodgers     .714   .691    .023
Giants      .705   .685    .020
Yankees     .699   .682    .017
Pirates     .691   .675    .016
Rockies     .690   .678    .012
Tigers      .696   .685    .011
Twins       .692   .687    .005

While that 31-point improvement doesn’t top the record-setting 54-point improvement achieved by last year’s Rays, it would tie for the eighth-largest year-to-year increase in the Retrosheet era (since 1954), a tidy accomplishment. The improvement isn’t solely due to [Elvis] Andrus, who ranks fourth among major league shortstops in Fielding Runs Above Average (+13) and Plus-Minus (+11 runs), and second in UZR (+10.1). Ian Kinsler (+16 FRAA/+7.5 UZR/+16 Plus-Minus) outdoes Andrus by some metrics, and right fielder Nelson Cruz’s numbers are particularly off the charts in both FRAA (+21) and UZR (+13), though they weigh in more conservatively at +7 in Plus-Minus. While the magnitude of his contribution may be in doubt, there’s no question that Cruz deserves at least some of the credit for the fact that the team ranks sixth in slugging percentage in balls in play after ranking last in 2008, as Matt Swartz noted last week.

…Also particularly notable among the improved defenses are the playoff-bound Dodgers and Yankees. Rafael Furcal’s return to regular duty, the upgrade from Jeff Kent to Orlando Hudson, and a surprisingly strong season with the leather from Casey Blake have made the difference for the former, particularly in helping Randy Wolf place 11th in the league in SNLVAR via a league-low .254 BABIP. As for the Yanks, they owe their improvement to the arrivals of Mark Teixeira and Nick Swisher, the departures of Jason Giambi and Bobby Abreu, the increased presence of both Brett Gardner and Melky Cabrera, and a surprisingly strong season from Derek Jeter. Their Park Adjusted Defensive Efficiency (-0.14) shows that they’re basically an average unit at best.

Which puts them ahead of their AL East rivals; indeed the division seems to be leaking defense, given that the Rays, Red Sox and Blue Jays all rank among the six teams with the largest declines from last year. In Toronto, center fielder Vernon Wells is as much of a drag in the field (-6 FRAA/-18.3 UZR/-17 Plus-Minus) as he is on the payroll. In Tampa Bay, the Rays have dropped back to the middle of the pack after last year’s turnaround; the various fielding systems differ as to where the responsibility for that lies, with Jason Bartlett, Carlos Peña and B.J. Upton each showing up as solidly below average in two of the three major ones.

Because they’ll have to live with their defense beyond this weekend, it’s the Red Sox who are of the most interest from among this group. Shortstop has been the team’s Achilles heel; in the absence of Jed Lowrie, they’ve gotten below-average work from Nick Green, Julio Lugo, and Alex Gonzalez. The team’s BABIP since acquiring the supposedly slick-fielding Gonzalez in mid-August has risen from .314 to .325, and that’s with the departures of John Smoltz and Brad Penny, who were doing little more than tossing BP while in a Boston uniform. Mike Lowell hasn’t been the same since hip surgery, declining by 27 runs according to FRAA, 21.6 according to UZR, and 22 according to Plus-Minus. The outfield’s been a problem as well, with Jacoby Ellsbury falling off a whopping 38 runs according to FRAA, 18.6 runs according to UZR, and 14 according to Plus-Minus. Don’t even ask about the catching situation, which doesn’t figure into Defensive Efficiency but which rates as a major concern given their upcoming first-round matchup with the fleet-footed Angels.

At the end of the piece I examine the expected regression to the mean of the 23 teams who improved by at least 26 points from Year 0 to Year 1 and played full schedules in Year 2 (i.e., no strikes, or at least none longer than the 1972 one). Eighteen of the 23 teams declined, and two more were within a point of doing so; the average decline from Year 1 to Year 2 was 10 points. Even so, only one of those teams actually lost ground from Year 0 to Year 2, and the average gain across that two-year stretch was 19 points — a mark we can expect the Rangers to better in 2010 given the return of Elvis.