There is only three modes:
Exhibition is a cut-and-dry one game affair.
Season can be expanded across a full season with your chosen MLB team; you won't be able to tweak player line-ups.
Post-Season, it automatically puts you in the chase for the Pennant. Be sure to check all of these out, as they offer some great fun for baseball players.

Embark on an inspiring mission of human connection beyond the UCA. Sam — with companions by his side — sets out on a new journey to save humanity from extinction. Join them as they traverse a world beset by otherworldly enemies, obstacles and a haunting question: should we have connected?