FanGraphs takes a look a sabermetric-heavy look at Pedro's staggering numbers against the Cards. Alvarez has a 1.7 WPA against the Cards this season. Only four times has a player had a season with a WPA over 10, three by Bonds, one by McCovey. Over a 162 game season, Alvarez's numbers against the Cards would translate to a WPA of 18.4.
Even better, since Pedro's numbers are team-specific against St. Louis, he is personally responsible for about a +3.5 game advantage for the Pirates over the Cardinals.