Which Qb starts the post season?

 Due to Derek Carr's season ending injury, Matt McGloin started on New Year's day for the Raiders but he didn't stay in the game. McGloin left with a shoulder injury in the 2nd quarter. McGloin finished his day with 54% completion rating and passed for only 21 yards. 

With Carr out and McGloin out for the rest of the game that left, rookie Connor Cook. Connor Cook came into the game and threw for 121 yards, 1 touchdown, and 1 interception. Cook finished the game with a 66% completion rating. 

So what now? As of 1:15pm eastern time, McGloin is listed as questionable. The Raiders are also rumored to be signing Garret Gilbert to the practice squad. The Raiders have a tough choice to make as they prepare to face the Texans in a wild card matchup. Do they risk re-injuring McGloin, that is, if he is able to play by then or do they play the rookie, who seemed to have a good feel of the game? Also take into consideration that they are playing the Texans and they themselves are having Qb troubles. 

In my opinion, Raiders should invest a reasonable amount of time in Cook and Gilbert (depending on if they sign him and if McGloin is healthy). The biggest mistake the Raiders could make is to train and practice these Qb's as a regular situation because this is preparing for the playoffs, all bets are off and it's time to get going. There is nothing normal about this for the Raiders because it's their first time in the playoffs since 2002.  So the Raiders shouldn't treat them as if they are Derek Carr, is what I'm trying to stress.