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DER（Defensive Efficiency Rating）

Defensive Efficiency Rating is the ratio of team defensive outs recorded in defensive opportunities. To determine Defensive Efficiency Rating for a team, divide the total number of hits in play allowed (not including home runs) by the total number of defensive opportunities (all balls hit into play, not including home runs) and subtract from one: 1-((H-HR)/(PA-HR-BB-HBP-SO)).

這數據主要是用在「團隊守備」上，簡單來說就是「被打進場內的球，有多少被守下了」。