Fangraphs.com has its weekly article commenting on the latest UZR (Ultimate Zone Rating) defensive measures. The Astros' team defense, based on UZR, is among the best at the moment:
Speaking of the Mariners, they are now back on top of the team UZR leaderboard, slightly ahead of the Rays. The Rangers, Brewers, and Astros (!?) round out the top five. The Orioles, Mets, White Sox, Marlins, and Indians are using oven mitts in place of gloves.
How do you like the parenthetical after the Astros? The Astros were a good defensive team last year, and if anything, the team this year, with the removal of Wigginton's glove, looked to be better.
The listing for Astros' players' UZR results is here. Matsui at 2d base, both Blum and Keppinger at 3d base, Bourn in CF, and Pence in RF are all doing outstanding jobs on defense, according to UZR. Tejada, however, showed a decline last week, which bears watching.
Revised Zone Rating (RZR) is another measurement system for defense, which is shown on the Hardball Times stat page. Currently, Michael Bourn has the highest RZR score in the major leagues at any position. Since Bourn's RZR is perfect (1.0), he can't get much better. Matsui is the second best NL second baseman, and Blum is the second best NL third baseman, according to RZR.