Jose Mourinho's eye for small details at Chelsea makes big difference against Manchester City

There are few individuals left at Chelsea who pre-date the Roman Abramovich regime of the last 11 years, but the masseur Billy McCulloch has been there since 2001 through nine different managers. He is an uncomplicated soul, who happily assumes the role of court jester, but is also regarded as one of the best when it comes to massaging some of the most expensive glutes, calves and lats in English football.

No manager under Abramovich has ever dreamt of moving him on, not least for the fact that he has proved consistently popular with the dozens of famous footballers Chelsea have signed over the years. As well as taking care of their aching muscles, McCulloch is on hand to slake the modern footballer's unquenchable thirst for the dreaded "banter". Entrusting him with the team talk, however, is not a move to which any of Jose Mourinho's predecessors in the job have given consideration.

As ever with Mourinho, nothing is quite as it seems. His disclosure that he left the team talk to McCulloch came when he was asked about specific tactics in his press conference after Monday's win over Manchester City. Mourinho was not so much looking to make an overnight star of McCulloch as create a useful diversion. The Chelsea manager revels in his status as the Jedi Knight of tactical innovation, but he is never keen to divulge the precise details.

The moment in the Etihad press room brought to mind other occasions over the years when Mourinho has been asked what his legacy to coaching will be. In his first spell at Chelsea he would describe how every training session he had ever taken, and every match-day team he had ever set up, was recorded in notebooks. Notebooks that, he added, would only ever be seen by his son, Jose Jnr, who, at 14, is a long way from becoming the third generation of managers from the Mourinho family.

Since he returned, Mourinho has claimed a new openness. In pre-season he discussed his pride in the Premier League managers who had graduated from his staff – Steve Clarke, Brendan Rodgers and Andre Villas-Boas. Mourinho said that all had been given access to his methods and ideas, but added for clarity that there was only one original, "they can never put a pen drive [USB stick] in my brain".

He is a difficult one to read at the best of times, even for those who spend most of their working day around him. In the second half on Monday, he snapped at his assistant Steve Holland, who had tried to get Oscar ready to come on too quickly for Mourinho's liking. As he took his rebuke, Holland's resigned expression was that of a man whose only aim in the first place had been to do the bidding of his boss.

Afterwards, Mourinho mentioned how he had sent on Demba Ba in injury time with the instructions that he should "mark Joe Hart if he comes up for corners". These are the details that matter and, as it turned out, Ba's sole contribution was a clearing header as the pressure increased late on. Once again, it was Mourinho who had all the marginal gains.

Nemanja Matic, one of many in Chelsea's side who outperformed his City counterpart, said that the preparation had been vital. "We prepared very well," he said. "The coach showed us some videos of Manchester City and, of course, they showed the quality they have, but also where they make mistakes. We cannot say what we prepared because it is only for us, but the preparation was very good and of a high quality.

"To play in a game like this he prepared us very well, as you saw on the pitch. Everyone knew what they were meant to do, which is why we got the result."

It was a classic Mourinho game plan. There was a specific job for every one of his outfield players when the team were in possession of the ball, and then, just as importantly, a critical role to play when they were without it. Space was closed off to City, starting from the front with Samuel Eto'o, but especially with Eden Hazard, who shut down the channels that Pablo Zabaleta and Jesus Navas usually exploit.

"We spent a couple of days on it," John Terry said, "and this is where he [Mourinho] comes into his own, working on their strengths and weaknesses. They were long sessions for us but very worthwhile."

When Chelsea did manage to steal the ball and break forward, Mourinho would direct Matic and David Luiz to hold their positions. He permitted the front four to commit to the attack, and occasionally one full-back, but in all respects the system was king. Chelsea had to ride their luck when City created chances in the first half but for long periods of the game they looked comfortable, in spite of having a vastly inferior possession count.

One of Mourinho's strengths, according to players, is that he often correctly predicts the ebb and flow of a game in his pre-match briefings: when a team is likely to become tired; the likelihood of one opponent to make a mistake. Samuel Eto'o credited Mourinho with encouraging him to pressure Timo Hildebrand in the Champions League game against Schalke this season. The goalkeeper duly lingered too long on the ball, striking it against the advancing striker, from whom it bounced into the goal.

No one would claim Mourinho is perfect. But Monday night showed the team is changing, evident in his decision to leave Frank Lampard and Ashley Cole as unused substitutes. Overall, the result added to the lustre of his reputation as the manager who can pull off a big result. And Mourinho's reputation, his image, has always been crucial to him. Not least as one more weapon in his armoury.

That team talk: Who is 'Bill Blood'?

Billy McCulloch, also known as "Bill Blood" by the Chelsea players, is rated highly for his qualities as a masseur. He also does an occasional turn on Chelsea TV, telling weak jokes badly. He remains hugely popular as the target for training ground practical gags. Under Mourinho's first regime McCulloch, from Swindon, would do stand-up routines at pre-match meals. He is also a devotee of tai chi.