Sometimes things just no longer work. See Dortmund last season under Klopp.
But we aren't like Dortmund or other teams, if we let Jose go we are going to continually stay in this cycle of sacking managers which meant we won't the league once in 8 years or something, thats not good enough for us or shouldn't be.
We need to back the manager, players have too much power and its not a good cycle to get into at all.
That said the manager has to improve, Ivanovic needs to be dropped, Azpili returned to right back and Baba at lb, Zouma has to play as well, i'd personally pick the captain to lead the line in defence, he'd probably chop off a finger to get us out of this mess.
4-2-3-1 isn't working right now, we need to revert to 4-3-3, focus on being tight at the back and defending in numbers, RLC with Cesc and Matic (or Ramires if he wants to drop one of them), pick two wingers with Costa up top.