The upper reaches of the Premier League are once more a place of fascination and fallibility. This was Manchester City's first defeat in this competition since last season, when they were overcome at Everton on 7 May. They were hampered by the dismissal of the left-back Gaël Clichy with a second yellow card after he had fouled Ramires in the 58th minute.
City lead the table by a mere two points, much to the satisfaction of a pursuing Manchester United. That, all the same, was an irrelevance to everyone at Stamford Bridge. The gap that Chelsea must close does still stand at a substantial seven points but outcomes of this sort should galvanise the squad and enhance the authority of the manager, André Villas‑Boas.
While there is a great deal of interest in seeing just what the Portuguese can achieve with the club, victory came with a penalty converted by a veteran who had been brought on from the bench. That description of Frank Lampard will scarcely please him but his cameo was decisive as he crashed home a spot kick in the 82nd minute that settled the outcome. At 33, he at least had the experience to disregard his failure with a penalty at Newcastle United.
The opportunity for Lampard arose because Joleon Lescott's left arm had been raised as Daniel Sturridge's drive was blocked by it. In struggles between well‑matched sides, grievances and complaints are natural. City, who had gone ahead at the outset, should have had an invitation to extend that lead. The referee, Mark Clattenburg, somehow judged the contact insufficient for a penalty to be given after 14 minutes when José Bosingwa connected with David Silva.
City will have difficulty purging that episode from their minds. As it is, Roberto Mancini's team are still in the lead; they will have enough sense to appreciate that they are ahead and will not be going to Old Trafford, where they ran amok, or Stamford Bridge again in the league this season.
It says much for City that Chelsea, with such means, were close to being regarded as underdogs in the buildup to this match. Mancini will have to live with the unavoidable expectations.
Villas-Boas, for his part, has had the type of memorable impact that will strengthen the bond with the Stamford Bridge crowd.
With Chelsea topping their Champions League group while United and City were eliminated from the tournament, there is a sense of status about the Portuguese and his squad. That, in turn, should be enlivening for the Premier League as a whole. Victory over Valencia had been achieved with cunning as Chelsea won with a counterattacking style. Villas-Boas, in his analysis and tactical decisions, can be intriguing.
Even so, he may have felt powerless in the second minute of this encounter. With John Terry pushing up, Sergio Agüero released Mario Balotelli on the right and he resisted a challenge by Branislav Ivanovic before rounding the goalkeeper, Petr Cech, to finish.
But there was nothing tumultuous about the contest then. Chelsea continued to be methodical since most of the match lay before them. The crowd were merely subdued, as if awaiting further clues. When Didier Drogba did let fly from the fringes of the penalty area in the 25th minute the save by the City goalkeeper, Joe Hart, was unremarkable, even if he did concede a corner.
With City relishing their lead, the pressure bore down on the hosts and, to a degree, their manager. His reaction in this instance helps explain why the owner, Roman Abramovich, is content to give the newcomer time and also accounts for the fact that he agreed to pay Porto £13.3m for Villas-Boas.
Another style was demanded in this match to that which succeeded against Valencia. Chelsea drew level in the 34th minute. Terry picked out Sturridge on the right and he easily beat Clichy before his low centre was converted with force on the volley by Raul Meireles. All in all, the occasion had not been prone to hysteria. That may reflect the fact that these are managers at least striving to be measured in their behaviour. Each of them appreciates just how much hyperbole can sweep over them because of public's fascination with the budgets being authorised for this apparent struggle for command of English football.
Despite the intensity, this may be only a little episode in the tale of the clubs. Defeat is scarcely welcome for City but talk of invincibility is a sort of distraction and the side can now get back to a more normal life, even if they cannot find it easy to thank Chelsea for taking away some of that intense focus on them.