An unearned run is any run that scored because of an error or a passed ball. Oftentimes, it is the judgment of the official scorer as to whether a specific run would've scored without the defensive mishap.
The purpose of the unearned run is to distinguish which runs a pitcher is at fault for allowing. Unearned runs do not count against a pitcher's ERA. However, there are a few flaws with ignoring unearned runs when evaluating a pitcher. First, it's a pitcher's job to prevent runs -- not to simply prevent earned runs. Second, not every error is created equal -- and some plays that are ruled as hits can be a product of subpar defense.
Although unearned runs don't hurt a pitcher's ERA, they can hurt a pitcher in other ways -- namely in his quest to win. Every error means a bigger burden on the pitcher in terms of pitches thrown. In this regard, unearned runs can often lead to an early exit for a pitcher.
An unearned run can never take place without the occurrence of an error or a passed ball.
In A Call
"cheapie," "run scored due to error"