Mourinho’s fate is inexorably linked with that of his Brazilian-born superstar.
Costa, returning from a three-game suspension, scored one, shot for Alan Hutton to score an own goal and put in an admirable shift that included his characteristic, game-long playground feuding with opposition defenders.
On this occasion, there seemed some merit in Mourinho’s claim that the likes of Villa’s Micah Richards and Ashley Westwood were the real villains of the piece, attempting to provoke a reaction from Costa which was not forthcoming.
But, given the lack of quality in Chelsea’s striking corps - the unconvincing Loic Remy, the semi-retired Radamel Falcao and … nobody else - Mourinho can only hope that this is a new leaf being displayed by Costa.
“Of course we need him,” said Mourinho. “When you lose him we’re a bit in trouble because the team always depends on a striker like him, from a character and personality like him. So when we don’t, of course we miss him.
“I’m pleased he didn’t react, but I would be even happier if the people who find his hypothetical or real negative moments were honest the other way, and show and show and show.
“He will get that until the moment people point the finger at them and show the images, re-show the images and have the top pundits speaking about it. At this moment he is the bad guy and if you are telling me here that this happened and are already saying that in the next matches they will do the same it is something that is easy to understand. If it’s easy to understand, then show.”
For all of Mourinho’s martyr complex, it is not difficult to have a degree of sympathy for his position. Costa may have “previous” in the off-the-ball department, and a sullied reputation that is well merited, but that should not deny him protection from the sort of provocative treatment of which he has been guilty in the past.
“Let’s see what happens,” said Mourinho when told that video footage seemed to show Westwood manhandling Costa in an attempt to rile him.
When it was suggested that the authorities will do nothing, Mourinho could only agree: “No. I know.”
Still, the Mourinho chip was on full display when asked what Costa may have learned following that suspension for his antics in the stormy London derby with Arsenal.
“What you learn is the big desire for people to find the negative things on him,” said the Chelsea manager. “He clearly knows that.
“But the character, the personality, the movement, the starting pressure high up to stretch the game when the team is under pressure, to ask for the ball in the space, to let the team come out of the pressure zones. He has a lot of tactical quality the team needs.
“He is a good player. Sometimes personality qualities add something to the team. When you speak about leadership, when you like to speak about players because of their age, their experience and the armband. That’s what you try to find - different leaders in teams.
“Diego isn’t a leader in the dressing room - he doesn’t even speak English well to be fluent - but in the game, the way he plays, the way he gives his body to the cause - it is always punished - is brilliant.
“That’s why he is Diego. He is an influence.”
And, on Saturday at least, a positive influence. Until his 34th minute opening goal, courtesy of a dreadful clearance from Villa goalkeeper Brad Guzan and slip by defender Joleon Lescott, Chelsea’s nerves were apparent and raw with the visitors creating as many, if not more, opportunities.
But Costa’s finishing proved the difference between the teams, even if his second goal after the restart required a huge deflection, and left Villa’s under-pressure manager Tim Sherwood with many questions and few answers. At least the Villa supporters remain firmly in the beleaguered manager’s corner and sang his name throughout the game.
“Let’s get one thing straight: we are on the same side,” said Sherwood. “They know that if anyone is going to be fighting for them then I think they would quite like to have me in their corner.
“I’m trying to find the right formula, we’re a team in transition with a young group of players. It’s obvious for everyone to see, it’s quite clear. I’m trying to instill in them not to be scared to lose. If anyone should be scared to lose then it should be me. But I’m not. I want to go out on the front foot and if I die, I die on my sword.”
Begovic 6; Azpilicueta 7, Zouma 5, Terry 6, Baba 5; Ramires 7, Fabregas 7; Willian 9 (Remy 90), Loftus-Cheek 7 (Matic 46, 7), Pedro 7 (Hazard 83); Diego Costa 8.
Blackman, Oscar, Mikel, Cahill.
Guzan 4; Hutton 5, Richards 6, Lescott 5, Richardson 5 (Amavi 64, 6); Westwood 5, Gueye 7; Gill 6, Grealish 8, Ayew 7 (Traore 68, 6); Gestede 6.
Bunn, Bacuna, Sinclair, Sanchez, Angel Crespo.
R East 7