The champions are 16th in the Premier League after Southampton on Saturday inflicted a fourth loss in eight games.
Terry started for the second time in six matches but the now familiar defensive failings were all too evident, leading to speculation Mourinho might be sacked, like many of his predecessors.
The Blues boss has repeatedly denied fractures in relationships within the squad, particularly with Terry, who has now publicly spoken of his support for Mourinho.
"We have a big group of players and we have the best manager who we remain behind and we remain together," Terry told chelseafc.com.
"That is what you do in tough circumstances
I have been here a long time and I have seen managers come and go and if anyone is going to get us out of this hole it is going to be Jose Mourinho.
"And the players will remain together and fight, and keep fighting for the supporters because they were excellent on Saturday."
Chelsea paraded the title and the Capital One Cup through west London just five months ago and the speed of the decline is alarming
Terry reckons a lack of confidence is a major factor, but maintains there will be a response from the players
"We are not in the familiar position we are normally in," the 34-year-old added
"We find ourselves in it and it is down to the group of players and the manager to get ourselves out of it and we must do that very soon.
"Generally I think we are looking low on confidence but we have a big group of players in that dressing room and we need to stand up, which we will do
There is no difference from last season.
"We need to be hungry like we were
Like many teams find, it is difficult to come back after winning the Premier League, we have seen it with Man City
"We are suffering a bit of late but we have big characters in the dressing room and we will remain together along with the manager and get ourselves out of this."
Chelsea resume after the international break at home against Aston Villa on October 17
"Once you can get one win you build on that," Terry added
"We must win at home to Aston Villa after the international break, which is maybe a good opportunity for players to go away and clear their heads and come back after that and really kick on, because we need to start winning football matches."
Source : PA