I would say it isn't different. If there were a hard "rule" that you cannot lose a starting position because of an injury, then the length of the injury wouldn't matter.
Coaches should start someone based on the person who provides the best opportunity to win. Whether that is win this game, or win sometime in the future is also a coach's decision. Fans don't see what happens in practice. Fans don't know how the players are performing on the field compared to the expectations that the coaches have. Being "named" a starter earlier in the year shouldn't have any more to do with the decision about who should actually start than the fans' opinion of who the starter should be. The coach should make the decision based on best opportunity to win. The coaches will be judged by winning or losing and not by who the starters were.
I think that CGC's opportunity to play for wins in the future is running out. Not saying that he should be fired right now, just saying that his runway to start taking off is getting near the end. I said in a different thread that I think the real time to take a look at progress of the team will be this week and next week. The coaches should play whichever QB they think will provide the best opportunity to win against UNC, and then against Pitt. Being named a captain and starter at the beginning of the year isn't as important as the best opportunity to win the game this weekend. Being the fan's pick isn't as important as the best opportunity to win the game this weekend.