It's obviously too early to start dancing on Jose's grave - the loss last night was very unexpected, particularly in light of the Everton result but clearly isn't a sign of the apocalypse at Stamford Bridge. They should still breeze through the group, making last night look somewhat irrelevant in terms of the result. An even slightly tougher group might've made things interesting though.
I still think that Jose is more secure than any manager has been in that job for ages. The club is all about Roman, we know that, but with Jose it's really the first time that Roman has had to basically admit a mistake by bringing him back. I think that gives Jose tremendous power, which I think will become more obvious when he next gets to play with Roman's chequebook.
This Mata situation is interesting though. I thought things were being overstated about Jose not fancying him, particularly given that Mata had actually been injured and thus not available. It'll be interesting if Mata continues to be somewhat relegated in the team selections going forward, particularly as Mata doesn't seem the type to rock the boat. In the past Mata has seemed obviously happy at Chelsea, or at least happy with the wage Roman pays him - I can't see him suddenly causing trouble given that at times he's seems the only sane one during some of the circus times there in recent years.
As for their title credentials, I still think it's too early to judge both City and Chelsea entirely until after the January window. With their respective owners things could be very different after that window. Only after that can we say for sure who is or isn't a title contender (assuming those two and United will be relatively close to each other in the title race). Until then I think the first El Plastico meeting will be very interesting - Chelsea have been dominated by City in terms of results in those games recently, but I think Jose could excel in those type of games.
Regardless, nobody can write Jose off this early, however enjoyable it is to see him stumble.