Well, it’s Achilles as a ghost (he died way back in the Iliad), so it’s not exactly an action role.
They should have given her a pair of Nikes and cast her as Hermes.
Unless it’s a flashback, or something at the beginning of the movie setting the stage for the return home. If Odysseus is returning from the Trojan War, they might include a snippet of it.
I vaguely recall that the TV miniseries did that.