Kammala wannan jumla: Giants sun sake lashe NL West a shekarar 2012. Casilla ya bayyana a duka wasanni biyar na NLDS da Cincinnati Reds. A Wasan 1, ya zo tare da San Francisco a baya a cikin na tara kuma ya ba da gudummawa biyu, kodayake an sami guda ɗaya kawai, yayin da Giants suka rasa 5-2. Koyaya, bai ba da izinin gudu ba a cikin sauran wasanni huɗu, yayin da San Francisco ya lashe jerin a wasanni biyar. A cikin
NLCS a kan St. Louis Cardinals, Casilla ya buga a wasa na shida a jere a cikin wasa na 1, bai buga a cikin uku masu zuwa ba, kuma ya buga a cikin uku a jere don kammala jerin. Bai ba da izinin kowane gudu ba, yayin da San Francisco ya tashi daga rashi na 3 zuwa 1 don kayar da Cardinals a wasanni bakwai. A kan Detroit Tigers a Game 2 na 2012 World Series, Casilla ya sauƙaƙe Madison Bumgarner don fara na takwas tare da Giants da ke jagorantar 1 <unk> 0. Ya jefa wasan da ba a zira kwallaye ba, yana taimakawa wajen kiyaye nasarar 2 zuwa 0. A Wasan na 4, ya zo tare da fitarwa biyu a cikin na tara kuma ya sa Gerald Laird ya yi ƙasa don kawo ƙarshen wasan, sannan ya ci nasara bayan Giants ya zira kwallaye a cikin na 10, yana share Detroit Tigers don lashe jerin.