One of the great things about watching a baseball game play out over a 3 and 1/2 hour period of time is the inevitable ebb and flow of momentum as the game progresses. There is an almost poetic rhythm to each nine inning contest.
Sometimes it’s dominated by starting pitching on both sides with microscopic opportunities shaping the outcome, getting more important as the game nears its conclusion. Other times the offense creates a back and forth battle more reminiscent of the punch-counterpunch activity of a basketball game.
No matter how a game plays out, there will be times that your heartbeat raises with every pitch and occasions that you find your hopes raised only to watch them dashed minutes later.
At it’s base level a game’s momentum is captured in your traditional line score as you can see the score change inning by inning as the game advances. But a line score doesn’t show you the intricacies of the activity within an inning. It doesn’t portray the concept of opportunity lost by runners left on base after a potential rally ends or snuffed out by a great defensive play.
This detail within a game may very well be considered its pulse. Each team’s lifeline strengthens and wanes as it advances players from station to station along the basepaths. If a game does in fact have a pulse, than Win Probability Added (WPA) is it’s electrocardiogram (EKG).
Win Probability Added as defined on Wikipedia is “a technical baseball statistic which attempts to measure a player’s win contribution by figuring how much each specific play he made altered the outcome of a game.”
Fan Graphs, a brilliant site managed by David Appleman, tracks WPA on a game by game basis. He provides a more detailed explanation of WPA.
“WPA is the difference in win expectancy (WE) between the start of the play and the end of the play. That difference is then credited/debited to the batter and the pitcher. Over the course of the season, each players