Throughout the six years since Jose Mourinho's departure from Chelsea, the ghost of the Portuguese manager has haunted his successors. When Andre Villas-Boas was struggling to get the squad on board with his project, his former President at Porto explained one of his problems. "He needs time to mould his own team," said Jorge Nuno Pinto da Costa. "And he can't do that as long as there are players, as I've heard, who exchange text messages with Mourinho. And Roman Abramovich knows this."
Mourinho's spine of Petr Cech, John Terry, Frank Lampard and Didier Drogba remained intact until last summer and his general footballing principles have been obvious throughout that period too. Mourinho's Chelsea were about power rather than guile, and arguably only the signing of Juan Mata in 2011 made the Blues a more artistic, inventive side.
Throughout the past couple of years, there has been a mini-revolution in terms of Chelsea's playing staff. When Mourinho's Inter defeated Chelsea in 2010, he noted that the majority of Chelsea's starting XI, aside from Branislav Ivanovic, was there during his reign. Now, that's far from the case. Since then, Chelsea have added David Luiz, Oriol Romeu, Ramires, Fernando Torres, Juan Mata, Oscar, Victor Moses, Eden Hazard, Marko Marin, Gary Cahill, Cesar Azpilicueta, Yossi Benayoun and Demba Ba to the squad. Other newcomers such Kevin De Bruyne, Thibaut Courtois, Lucas Piazon and Romelu Lukaku could return from loan spells.
The majority of those players are technically skilled attackers that might not have flourished in Mourinho's first spell in charge, when Chelsea were based around solid defensive positioning and lightning quick counter-attacks but it would be unfair to suggest Mourinho is too much of a defensive coach for this group of players.
At both Inter and Real Madrid, counter-attacking has been a key part of his armoury, but Mourinho has generally fielded four outright attackers at both clubs in his second season at Inter he switched to a 4-2-3-1 system that usually featured Wesley Sneijder, Samuel Eto'o, Goran Pandev and Diego Milito. At Real, his quartet was Angel Di Maria, Mesut Ozil, Cristiano Ronaldo and either Gonzalo Higuain or Karim Benzema.
Granted, sometimes these players have been used in defensive roles: Eto'o and Pandev played very deep in the latter stages of the Champions League, while Di Maria dropped back to assist his fellow midfielders, allowing Ronaldo to stay further forward. But Mourinho has been flexible with his systems, and the amazingly defensive Inter performances that secured their European Cup win were significantly different from the displays on route to the Serie A title.
Mourinho will have no problem incorporating four attackers in his new-look Chelsea side although someone like Oscar might find himself in a functional wide role and just as Mourinho embraced the central playmaking talents of Deco, Wesley Sneijder and Mesut Ozil at Porto, Inter and Real respectively, a player like Juan Mata could become Mourinho's key man.
In terms of embracing his new charges, however, Mourinho's true problem will be managing the experienced members of the playing staff. The character and leadership shown by John Terry and Frank Lampard was a key factor in Mourinho's success during his first stint in London; now, those players have declined to the point where they're no longer automatic first-choices, although both still have the ability to contribute, both in the dressing room and on the pitch.
When arriving in Madrid three years ago, Mourinho released Real's two longest-serving players, Guti and Raul (although he insisted he wanted to keep the latter) which marked a new era in terms of 'the group', as Mourinho often describes his squad. They were key characters in the dressing room although, somewhat inevitably, Mourinho then had significant problems with Iker Casillas, who became the longest-serving player, and club captain.
Mourinho is keen to guard against established veterans undermining him. The situation with Terry and Lampard is, on paper, not dissimilar - if it wasn't for Mourinho's previous relationship with both men. Neither will feature as prominently as in Mourinho's first spell in charge, but it's difficult to imagine either will be sold especially considering Lampard's new contract.
Perhaps the template here is Marco Materazzi who was rarely a starter during Inter's European Cup win, only playing 95 minutes in Europe during 2009-10 yet became so enamoured with Mourinho that he openly wept when the Portuguese coach departed (http://www.youtube.com/watch?v=tmiqUQFgOxE).
Mourinho has the capability to convince veterans like Lampard and Terry of their importance to the squad, despite handing them a reduced role. Although a shrewd tactician, Mourinho is primarily a keen psychologist; and while it's become a cliché to focus upon Lampard and Terry's influence, Mourinho's relationship with that duo will be crucial to his authority amongst the rest of the squad.