You can't blame Mou if they're dogshit..
You can, though. Not when they play a single poor match, but when they are clearly unable to get in good shape then it is only logical to blame the manager.
Just look at Guardiola at City. Gets to spend just as much as ManU (has spent slightly more), but actually has a plan, purchases players that suit that plan and now Man City is, again, #1 in the premier league. They arguably play the most attractive football aswell.