Vidic will join Inter Milan on a free transfer this summer.
He told Sky Sports: "What's gone wrong? There's been a lot of talking. We changed our manager and our director. It's been a transition.
"I am surprised (about how the season has gone). I knew it would be a hard season and we might not win as many trophies.
"The manager needed time to adapt to his players and the players need time to adapt to the manager. I didn't think it would be that bad."
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