One of the emerging themes of the 2012 season is the increased emphasis on defensive shifts by many Major League teams. When the WAR framework was originally developed, shifting was not as common, and the defensive metric included in WAR was not built to account for these kinds of shifts. So we've made an adjustment to the way we're crediting teams for their defensive contributions: the runs saved measure is now based on the rate at which teams turn balls in play into outs. We've included park factors to adjust for environments that inflate batting average on balls in play, and this way of measuring defensive contribution allows for a better reflection of a team's overall run prevention. You will note a few teams moved in the rankings this week due in part to this change. The Blue Jays -- jumping from No. 28 to No. 16 -- are the biggest beneficiaries of the adjustment.
The Rangers end up back atop the rankings, and for the first time all season, the Cardinals fell out of the top two. They've been displaced by the Washington Nationals, a club that even received a home run from pitcher Stephen Strasburg in Sunday's victory over the upstart Orioles. Given how many injuries the Nats have suffered, their early-season success is remarkable. It might not be a stretch: If guys like Mike Morse and Jayson Werth are healthy for the second half of the season, the nation's capital could have a legitimate World Series contender to root for in October.
NOTE: All stats are through Sunday, May 20.
Rankings written by Ben Duronio of Fangraphs.com. The system used to rank the teams is based not on the current standings or a gut feeling about team quality, but on how well they've performed at the underlying traits that predict future performance better than wins and losses.
wRC+ is an offensive index where 100 is league average and every point above or below that denotes how far from league average a player's performance has been up to that point. It is adjusted for park and league, so it takes into account the context of a player's surroundings, and allows for comparison of performance from players in different situations and in different times.
MLB Power Rankings