"I don't know yet," Shanahan said Thursday when asked who would start at quarterback. "We'll get a chance to see how Robert progresses during the week, and we'll make a decision probably on game day."
Keep in mind that Shanahan admitted Wednesday he would delay announcing the decision in order to keep the Browns guessing.
Based on Griffin's improved practice Thursday while nursing a lateral collateral ligament sprain, it's not hard to guess where this is going. Griffin is looking good in practice; it's hard to imagine he'll sit Sunday.