Again you're stating "huge amount of injuries" - there aren't. Two players are injured in his position. The squad is deficient in central midfield but it's not because of injuries.
My opinion is that he was finished about half-way through last season and basically limped on until the end before retiring with good grace. To come back now is folly on his and the club's part - his legs are done. The Guardian Football Weekly podcast (fairly reliable AFAIK) this Monday said he hadn't been training with the Man Utd first team - the first they knew about it was seeing him in the dressing room and on the team sheet before the City game.
Pogba has been making noises about leaving the club at the end of his contract, which expires in the summer, due to lack of opportunities. If all you need is a bit part player and you truly believe in your young player's potential, you wouldn't bring back a guy who retired bang on time. Fair enough point about his example in training, but he's been coaching since retiring, why not just stick with that?
I can see the potential positives in the deal assuming he's still at a decent level, but from watching him towards the back end of last season he really was so far gone that I don't think he's any better use than a kid, and at least the kid has the potential to improve. That's why I think it's stupid.
Fundamentally I think it comes down to you thinking he can still do a job that Pogba/Morrison can't and me thinking he can't. Think we'll probably have to agree to disagree on this one