We're told "A.I." staffers helped Casey up and put him in a chair so he could calm down.
Ironically, his song choice Thursday was "I Don't Need No Doctor."
Our "Idol" spies tell us ... Casey felt horrible that the judges used their save for him, saying "I feel really bad that other [contestants] might have to go home now because they [the judges] used the save on me."
Casey had a rough day Thursday. He got a blood transfusion in the morning because of ongoing problems with internal bleeding.