I don't think you can solely blame the manager although I agree that he can often play a major role. It's always a battle between players, managers and the medical staff around whether players are fit or not. Dr Batty used to consider all aspects when deciding if players could play. Even if a player wasn't 100% he would make a judgement and clear them to play if he felt that playing was better for them mentally and weigh that against the risk of aggravating the injury. What he wouldn't do is allow players to play when the risk outweighed the benefit, even if that risked upsetting Mancini.
If a player who was previously fit pulls up in training or the warm-up then that could be down to poor sports science or the way we train. I'm not an expert but I asked someone who was and they said that muscles can be made more resistant to tears with proper conditioning and the way we train has an impact on that. If he's ignoring what the medical and fitness staff are telling him then he has to carry much of the can. If they're not telling him the right thing then they have to take much of the blame.
So I may have been a bit harsh on Dr Sala and his staff although the fact our injury record in 2012/13 was significantly worse when we had the same manager but a different doctor makes me think I wasn't.