Look at it this way, he was already playing with cracked ribs while playing in the Bucs game two weeks ago and he started the 49ers game with those same cracked ribs. My guess is that had he not punctured his lung he would have come out of the locker room after halftime ready to finish the game last week. Drew said in the post game presser that his issues were "cumulative". I'm not saying that he should be playing after his three weeks on IR (or even that he will be able to do so)... but going by what we saw, if Drew can breathe at all, he will figure out a way to physically get the job done.
Of course I also believe the results of the next three games will have a lot to do with whether they will allow Drew to give it a try. I get the feeling that the way our backup QBs play will have a lot to do with that decision. :unsure: