Reports say that Bart has a herniated disc (otherwise known as a "slipped disc"). These types of injuries are tough to guess when it comes to predicting how long they will take to heal. If anyone suggests that this is somehow suspect, I would wonder exactly what kind of conspiracy they might imagine.
McCormack was, by all accounts, auditioned during the casting process and either refused the role or they felt he was not right for the role. As for any rumors that Esparza was considered, I suppose they may be valid, but I don't see him in that role. Just my opinion.
"Life is a lesson in humility"