(Jim McIsaac/Getty Images)

In 2009 and 2010, defense was an utter liability for the Nationals, who finished both seasons with the most errors in the majors. General Manager Mike Rizzo and the Nationals made a concerted effort to improve the defense before last season. And in 2011, the Nationals were drastically better. It has continued so far this season.

The Nationals finished the 2011 season with 104 errors — 16th fewest out of 30 MLB teams. This season, they have committed 57 (four on their just-completed 6-1 road trip) — the ninth fewest in baseball. As a whole, the Nationals are on pace to post their best fielding percentage since 2005. But all this tells only part of the story.

Defensive effectiveness is harder to quantify statistically. According to one highly regarded advanced metric, the Nationals rank middle of the pack. The UZR/150 measurement used by FanGraphs.com attempts to quantify how many runs were saved or given up and takes into account a total defense (range, errors and strength of arms). The value is weighed over 150 games.

The Nationals are 14th in the majors with a 1.0 UZR/150. Last season, they finished with a 0.3 UZR/150 (also 14th in the majors). The previous two seasons the UZR/150 values were negative and in the bottom half of the majors — meaning the defense cost the teams runs, and obviously, games.

So far this season, the measurement rewarded the Nationals for committing fewer errors than average (with Ryan Zimmerman at third base and Danny Espinosa at second base as standouts) and for above average range as a team (with Ian Desmond at shortstop and Bryce Harper at center field as standouts). They lose points for lack of strength in outfield throwing arms and lack of range in the outfield, particularly in left field. The Nationals also don’t turn a lot of double plays, and that’s likely because its pitchers are among the leaders in strikeouts.

The metric becomes a better indicator as the sample size increases over the season. But so far, it’s an encouraging sign for the Nationals that their defense has gone from liability to asset in a short time.

Of course, there’s room for improvement. Nationals pitchers, particularly the relievers, have done a poor job of holding runners on base, giving the catchers little chance at throwing them out. Only 13 runners have been caught stealing this season against the Nationals, who rank second-to-last in caught stealing percentage (16 percent). They also rank in top half in passed balls and wild pitches.

Manager Davey Johnson has often said an infield of Adam LaRoche, Desmond, Espinosa and Zimmerman is among the most talented he has ever been around.

Also impressive about the defense is that it has had to rely on rookies and backups because of injuries. Espinosa has filled in well at shortstop for Desmond, showcasing his tremendous arm strength, perhaps the best on the team. Steve Lombardozzi has shuffled between the outfield and infield. Tyler Moore learned a new position. The defense was also without Zimmerman, a Gold Glove winner, for a stretch.