The midfield has been altered most over the past year-and-a-half and Michael Essien is enjoying unique prominence. He is the only member of the squad who, starting with the Community Shield, has been in action for every second of Chelsea's 16 fixtures this season. Satirists might once have argued that this was merely a desperate attempt by his employers to get value for money.
No other club would have considered meeting Lyon's demand for ?24.4m in the summer of 2005. Essien, however, has turned into a force in the team's affairs as well as a raw powerhouse. The bottomless stamina is impossible to ignore but that alone did not make him the outstanding performer in Barcelona.
Mourinho still growls about the use of television evidence to impose a two-match suspension on the player for a bad challenge on Dietmar Hamann at the end of 2005. That ban surely rankles because it prevented Essien from facing Barcelona in the knock-out phase of the Champions League last season.
Mourinho had faith in Essien even then and few dissent now. "Michael is unbelievable," the manager said after Tuesday's game. "He's too strong for opponents. The way he plays is completely clean. Mikey had a very good game but this is the level he's been playing at since the beginning of the season."
Essien brought momentum to the side and Chelsea set about Barcelona with a gusto they had not shown under Mourinho in his two previous trips to Camp Nou. The 23-year-old had ample assistance. Even if the midfield who play ahead of Claude Makelele still do not dovetail as neatly as the manager would wish, Michael Ballack, Essien and Lampard make up a trio of daunting individuals.