How MLB's 'Fourth Out' Rule Allowed Red Sox to Score Confusing Run vs. Blue Jays originally appeared on NESN. As one of the hottest teams in baseball over the last month, the Red Sox rolled into Toronto on Monday night to take on the Blue Jays. Here's a look at the wacky run the Red Sox scored against the Blue Jays, why it counted and more. How confusing MLB 'fourth out' rule led to Red Sox run vs. Blue JaysA series of two plays in the top of the seventh sparked the confusion. MLB's "fourth out" rule is Rule 5.09©(4), which states that, when an appeal play takes place on an inning-ending play, "The appeal play decision takes precedence in determining the out."