The starters werer announced at a Monday afternoon news conference.
Detroit's Justin Verlander will oppose Cain.
Dickey reasoned his knuckleball could help dictate his place as a starter.
"If I'm brought into the game -- because you only have two catchers now, and Buster Posey hasn't seen me at all -- and all of a sudden here he is with seven warm-up pitches, that's a whole different animal," Dickey said Sunday of the Giants' All-Star catcher.
Dickey followed an offseason climb of Mount Kilimanjaro to rise to the top of NL pitchers, going 12-1 with a 2.40 ERA. Cain pitched a perfect game against Houston on June 13. Cain is 9-3 with a 2.62 ERA.
Information from The Associated Press was used in this report.