Empirically, at least, the Orioles look like an outstanding defensive team. But I thought it would be fun to take a quick glance at what the numbers say.
As Sports Illustrated recently noted, analysts have come a long way in their ability to measure defensive quality. Even 10 years ago, defensive stats were like first-grade finger paintings compared to the Van Goghs we had for measuring offense. But no longer. My favorite system of defensive statistics is John Dewan's +/- rating, which he created for his excellent book, The Fielding Bible. Dewan's company, Baseball Info Solutions, actually reviews every play made by every MLB defender and compares each one to a database of similar plays. The system then counts how many unusually good and how many unusually poor plays a defender makes. The difference between the two is expressed as a +/- rating.
The system rated Brian Roberts as an average to slightly above average second baseman in 2006 and 2007. But he fell to slightly below average last year with a -3 rating. He was solid on balls hit at him or to his right but poor on balls hit to his left. Roberts affords the Orioles a huge offensive advantage compared to other second basemen but might only help them break even defensively.
Melvin Mora rated as an average third baseman in 2006 and 2007 but plummeted to a -13 last year, 34th among regulars at the position. Anomaly or sign of decay for an older player? We'll see, but it's an area of concern, especially considering that Ty Wigginton has always been a poor defender at third, according to the system.
Aubrey Huff is hard to measure, because he has played only about 620 innings at first base over the last three years. He graded as a -2 for those innings. But Huff at first seems like decent idea under the defensive spectrum philosophy espoused by Bill James. James placed all defensive positions on a continuum, with shortstop the most difficult and first base the easiest. In general, he argued, good defensive teams have players at the easier positions who are capable of playing the more difficult ones. Huff wasn't a good third baseman, but the mere fact that he could play the more difficult position suggests that he's overqualified for first base.
Under the same principle, the Orioles are lucky to have Felix Pie, a capable center fielder, in left. Both Adam Jones and Nick Markakis rate as outstanding defenders at their positions, with Jones at +4 in 2008 and Markakis at +12. It's not exactly a shock to hear, but outfield defense should be a strength for this club.
At catcher, Gregg Zaun threw decently last year but hasn't thrown out more than 28 percent of base runners since 2003. If it's a comfort, he's no worse than Ramon Hernandez, whose throwing declined substantially after an excellent 2006. If the scouting reports are correct, Matt Wieters could solve this problem soon.
So in general, the numbers seem to support fan perceptions of the club's defense. The Orioles are sound up the middle and fast in the outfield with relative weaknesses at the infield corners. That's a pretty good defensive profile.