Opening Day, April 1, 2013 is 34 days away. There have been one hundred walk off home runs in Angels history. This is the story of #34, the greatest day on offense by an Angels player comes against the Yankees.

July 15, 1979 - This Sunday afternoon game was the climax of a three game sweep of the Yankees. Bobby Grich hit a walk off home run to cap the the single game record for best offensive performance in Angels history.

How does one measure the best offensive performance in a game? Garret Anderson once had ten RBI in a game, but most of them came after the Angels were way ahead - Since the Angels were already quite likely to win the game, one could argue that Garret's at-bats came in situations that were less important then other instances in other games when a player gets a clutch hit to come back from a a deficit, tie the game and /or go ahead. Even these walk off home runs are not all created equal. Hitting a walk off grand slam in a tie game with nobody out is not as impressive or impactful as hitting one down by three runs with two outs.

A stat has been developed to measure the impact of each play in a game. WPA stands for Win Probability Added. Starting each game as a 50/50 proposition, WPA measures each play in the game as adding or subtracting from a win. In this game, Bobby Brown (the Yankees CF, not the singer) led off the game with a ground out. The Angels then had a 52% chance of winning the game and the Yankees a 48% chance. The second batter, catcher Thurman Munson, singled. the probability of each team winning was then back to 50/50 - a man on first with one out in the top of the first gives each team the same chance of winning as if the game had begun. The third batter of the game, Chris Chambliss, hit a two-run homerun off Angels starter Dave Frost. The Homerun gave the Yankees a Win Probability Added of 17%. Suddenly the Angels only had a 33% chance to win the game.