Chelsea may have secured their passage to the Champions League last 16 on Tuesday, but their 1-0 defeat at FC Basel demonstrated that they remain a work in progress.
Chelsea had been stunned by Basel at Stamford Bridge in their opening group game and their defeat at St Jakob-Park was similarly galling, with the Europa League champions failing to record a single shot on target.
Ultimately it mattered not, as Schalke's 0-0 draw at Steaua Bucharest in the other Group E game guaranteed Chelsea's progress, but it was the latest in a succession of stuttering displays by the London club.
Having won all six of their games in October, they hit the skids in November, losing 2-0 at Newcastle United and needing a fiercely debated injury-time penalty to snatch a 2-2 draw at home to West Bromwich Albion.
Manager Jose Mourinho said the most recent loss to Basel could be explained by "fatigue", but he is yet to find a consistent winning formula since returning to the club from Real Madrid in June.
He was quick to settle on a 4-2-3-1 formation -- his "favourite system" -- but in Chelsea's first 17 games he has experimented with no less than 10 different combinations of players in the attacking midfield band.
Oscar, Eden Hazard, Juan Mata, Andre Schurrle, Willian and Kevin De Bruyne have been chopped and changed with dizzying regularity, with the same trio selected to start consecutive games on only two occasions.
In contrast, Mourinho had identified a favoured attacking midfield combination by his third league game at previous club Madrid, selecting Angel di Maria, Mesut Ozil and Cristiano Ronaldo for 11 successive matches.
Former Liverpool midfielder turned television pundit Jamie Redknapp identified the problem in September, saying: "I don't think Jose really knows what his best team is.
"If it wasn't Jose Mourinho, you'd probably be thinking: 'What is this guy up to? What's their best system? What's their identity? How do they play?'
Mourinho switched to a 4-3-3 system for Saturday's trip to West Ham United in the Premier League and was rewarded as a liberated Frank Lampard -- afforded more freedom by the presence of two central midfield players alongside him -- scored twice in a 3-0 win.
The same formation did not yield quite the same results in Basel, however, leaving Mourinho with a tactical conundrum ahead of Sunday's visit of Southampton in the Premier League.
Upon returning to Chelsea, Mourinho pledged that he would introduce a more proactive, passing style, but he is struggling to find an alternative to the counter-attacking approach that is his trademark.
Chelsea have averaged a healthy 56.9 percent of possession in their 12 league games to date this season, but they seem happier when they have taken an early lead and can pick off their opponents on the break.
Of their 12 victories in all competitions, 10 have come after they went ahead inside the first 33 minutes and on the five occasions when they have conceded the opening goal, they have come back to win only once, in last month's 4-1 win at home to Cardiff City.
Mourinho also continues to bemuse fans with his sparing use of the artful Mata -- Chelsea's player of the season for the last two years -- who has started in less than half of their matches to date.
Mourinho has questioned Mata's application when he does not have the ball, but with 25 assists over the previous two seasons, the Spaniard had established himself as the most prolific creator of goals in the division.
With Chelsea only four points behind Premier League leaders Arsenal and through to the knockout phase of the Champions League, there seems no cause for alarm, but if Mourinho seriously intends to change the club's playing ethos, his revolution has started slowly.