No it's not crazy. Being a coach means you should also have an alternative solution. Some kind of plan B. A change in case of and injury. You shouldn't go all in and at some point find yourself $#@!ed.
Since we converted to 4-2-3-1, we have been really thin in attack. Since Pjaca got injured (who Allegri trusted a lot from his comments) we have literally no attacking subs.
Allegri decided to keep this formation no matter how thin we might be. Fair enough. But now we have to really be careful. We have a lot of games to play and 3 fronts to compete.
So, what are our possible relatively good attacking alternatives? Pjanic as an AMC, Alves as a AMR, Sandro as an AML. I won't even put on the table Lemina or Sturaro as wingers, none wants to see stuff like this with Barca.
Alves is not very influential as an AMR these days (maybe Allegri also sees some psychological advantages in starting him). Pjanic on the bench is not a very good idea, he has become the centre of the team and a good free kick taker in such a tight match is always a good thing to have. Sandro is the only one who can come in fresh and create havoc. Or in case of an injury come in and not lose a lot in terms of quality. Maybe he is 100% sure that Mandzu can't last long. We don't know exactly.
Do you think that Allegri thinks Asamoah is better as a LB? I really doubt it. But since we are continuing with 4-2-3-1, we have to expect stuff like this and Stu/Lemina as wingers in league games and a lot of energy conservation. We can't do 7 (league) + 5 (CL best case) + 1 (cup) games with 4 guys, 2 of which are 29 and 30, playing every minute.
For me the best change in our situation would be to change to some kind of 4-3-3 (relatively good midfield with Marchisio back and 1 sub in attack). But fortunately, I am not the coach of Juve. So, in Max we trust..