What are the rules determining the winning pitcher?
The quick answer is – the winning pitcher is the pitcher whose team assumes a lead while that pitcher is in the game, or during the inning on offense in which that pitcher is removed from the game, and does not give up the lead. But like most things in baseball, there are a few exceptions… If that pitcher was the starting pitcher and the starting pitcher did not complete five innings of a game that lasted six or more innings on defense, or four innings of a game that lasted five innings on defense, the starting pitcher should not be credited with the win. In that case, the official scorer would credit the relief pitcher as the winning pitcher if there is only one relief pitcher. If there was more than one relief pitcher, then the relief pitcher who, in the official scorer’s judgment, was the most effective would be credited as the winning pitcher. It’s covered under rule 10.17 in the Official Baseball Rules.
