Here's the full statement in English on his personal website:
http://www.robertomancini.com/en/notizie-2/175-mancini-says-goodbye-zenit.html
He said in his press conference after yesterday's game that he'd decided to leave three months ago, and I'm sure he's had his eye on the Italy job for the last six months. I suspect that has contributed to a lack of focus on his part. He's also right that "Important injuries penalized the second part of our season" given that he lost his best defender and best striker to cruciate injuries. However, despite that, it can't be denied that the results have been well short of reasonable expectations.
He started well, but once teams started to adopt suffocating tactics against Zenit, he never worked out a way to combat that and the team never quite gelled as a cohesive unit. At the outset of the season, they were buoyed by the explosive goalscoring form of Russian striker Alexander Kokorin, but suffered as he first went off the boil a little and then sustained a serious injury. The feeling here was that Mancini was complacent when he accepted the job, handing the club a list of expensive foreign recruits and assuming that would be enough to win the league, without exam ining what would actually be needed in the particular context of the Russian league. I suspect that there's a degree of truth in this, too.
Ultimately, as someone who was very keen to see Roberto prosper, I've found the campaign to be a big disappointment, and I think it's fair to say that his reputation in Russia has taken a hammering. Elsewhere, I think it will recover easily enough if he does a decent job with Italy. For reasons we discussed when he first emerged as favourite for the post, there are grounds to think the job could suit him. Let's hope so.
Finally, as this will be my last post about Mancini at Zenit, thanks to all who've commented positively on here and via private channels about my updates on his fortunes through the season. As I said, I enjoyed doing them in any case but it's good that there were users of the board who appreciated them.