The guts madness has started. Getting hit by an arrow, falling down a cliff, resting the whole night in cold temperature, getting hit by multiple arrows again and still smashing the head of an 3 metes giant. That's guts for you.
Guts wasn't just trying to deflect the mace, He was trying to slice it into ribbons! Casca has learned the truth of how he's been protecting her all this time. Maybe her jealousy will finally fade