Honestly, what Mangala has that we lack is just that pure physicality to cover for our other defenders. So many times last year we conceded goals just by the opposition putting it in behind Otamendi or Kolarov and then it was game over, no one was getting back. When we had Mangala, he'd run like a madman and get back and try and at least make it difficult.
People slaughtered him for his passing and control, but it honestly wasn't bad at all, he was fine 99% of the time, but his lack of composure was the problem. If he made a mistake he'd lose his shit and start desperately trying to make up for it, usually leading to more. Otamendi probably makes twice as many mistakes, but shrugs it off and doesn't look like he gives a fuck that he's just made an arse of himself. Mangala on the other hand you could see how much it bothered him even by just looking at his face. He looked a lot worse on the ball than he actually was imo.
I'd have no problem at all with Mangala being here this year, but I don't remotely think he will be. I'd be more confident with him playing than Stones, but I know Pep feels differently
Not sure there is an argument for Nasri being given up on too soon, he was given more chances than just about anyone I've seen and continued to half arse it whenever he didn't feel like it.