Come on. I'm no trainer, but jogging back to the dugout didn't escalate his injury from "bad" to "season ending." In fact, it likely had no effect at all. I'm sure the trainers checked his knee, didn't detect anything right then and there, so they gave him a chance to test it out, probably even saying, "Look, if it hurts at all, don't be a hero." He tested it, it hurt, and he sat down.