As posted by Fabrizio, Nottingham Forest has parted ways with it's manager Nuno Espirito Santo, these's was a tense situation at the club between him and them, I believe that's the main reason why he was sacked. Nottingham Forest has started off this season with a win, a draw and a lose in three matches. I believe that's one of the major trigger as to why he and the club management has fallen off and it resulted in a sack.
It seems to me that this conflict between Espiritu and the management has been going on since the time when Nottingham failed to stay in the Champions League zone, then we all saw how a conflict took place on the field after the match. But for Espiritu it may be even better, because a coach of such a level will be able to achieve better results in a more ambitious team and I think that he will not remain without work for a long time. It is difficult when a team is left without a coach from the first games, but it is better to do it now than to work in such an environment.