A couple of points regarding Corrado.
It sucks for a player to sit - just waiting to get in the games when he has no control over the situation. On the other hand, he's making big money (not that he even thinks about that) and he's got a job he loves, on a team, hopefully, he also loves. He just needs to be patient and keep working and as Lou says, make the most of the opportunity when he does get in. He will get a chance, he will get in, but, this is very very typical (as we are learning) of MB's way.
Marincin is learning and he makes mistakes, as is Harrington, but MB keeps giving guys chances and keeps playing guys who make mistakes as long as they are learning and putting in the effort. So, taking out Marincin or Harrington in order to 'try out' Corrado for one game to see how he does is not MB' MO.
And, people fearing, that if he gets in a game and plays bad, he'll never get back in. ALSO, not MB's MO. If he puts in an effort BUT makes a few big mistakes, he will still be given a fair shake and another chance. We see this within the games with MB as well. Players make mistakes but they aren't punished if it was a mistake but not from lack of 'try'. It's another reason to not just put Corrado in order to see how he does.
There is upside to having Corrado sitting. It is a CONSTANT REMINDER to both of Marinicin and Harrington (and even Rielly and Gardiner - though I don't think it shakes there confidence all that much because they are confident in their games), there is Corrado sitting there waiting to take out jobs. Pressure, yes, but, they know what they CAN control and that is their 'try' and their preparedness. We see them making mistakes, the two young Dmen, but, they look pretty darn prepared each and every game and there is good reason that they are.
Edit: So, I don't think it's MB's style to put in a player for a game, then, if the game is bad, put in another player, and then, do it over. He totally wants to refrain from doing that. Maybe, he thinks about the fragility of both Harrington and Marincin's confidence. As long as they work hard and work the right way, - even if they make mistakes - they keep playing. If, if there is an injury and Corrado is in, then, he'll have that same strategy with Corrado.
Also, is Corrado on the right side? If he is, (i think he is) then, he's on the same side as Phanuef, Rielly, and Pollack. If he replaces Pollack, okay, so, he's with Harrington or Marincin, but it wouldn't make sense to replace Phaneuf or Rielly, so, anyone else, and somebody has to change sides; not easy - Rielly maybe can do it, but it wouldn't be a good situation for young Dman.
that's all i mean.
at 
