Defensive Efficiency Ratio is a statistic used to evaluate team defense by finding out the rate of times batters reach base, on balls put in play. Basically, for every ball hit into the field of play, how likely is the defense to convert that into an out?
The formula for Defensive Efficiency Ratio is: 1 – ((H + ROE – HR) / (PA – BB – SO – HBP – HR)).
This stat is frequently used because looking at a team’s defense just by their fielding percentage is very misleading. Due to things like widespread defensive shifts, it is becoming hard to know exactly how good or bad a team’s defense really is.