From the sound of it, the back was not an issue all week and didn't bother him. He apparently re-aggravated it sometime before the game (probably on a BP swing or something) and couldn't pitch. If that's the case, there's no sense in treating his back if it's not bothering him at all. I disagree with that. If your ace pitcher, who you owe a lot of money too, has to leave a game early because of back problems, it only makes sense to be precautionary and give his back some treatment. I dont care if Z said he felt better than ever, injuries dont usually just disappear, so be on the safe side and give him some treatment.