A £32m signing kicks a ballboy in the ribs in sheer frustration as another potential route to silverware slips away.
The disbelief on Eden Hazard's face at the red card that followed was presumably born of the fact he had made contact with some part of the ball but, regardless, this was a new nadir.
Too much of this term has been played out to a backdrop of exasperation. From Football Association bans to allegations against the referee Mark Clattenburg, the sacking of a manager who had just claimed the European Cup and the appointment of a successor loathed by a vocal and disgruntled support, the whole season has felt fraught. Then, 12 minutes from time, along came Charlie Morgan and Hazard, an ill-judged attempt at gamesmanship from one and a rush of blood that defied belief from the other, and the sorry script had a new twist no one had seen coming. This club still tend to monopolise the outrageous.
Hazard's indiscretion will dominate the aftermath but an aggregate loss to a side reestablishing themselves in the top flight may have damaging implications, too, for Rafael Benítez. The interim first-team manager had arrived at the club in November targeting silverware to restore his reputation and, potentially, earn a longer-term deal. He needed his own "Napoli moment" here, a rousing retrieval of a two-goal deficit, but that never really threatened to materialise. Swansea are rarely embarrassed on their own turf. This situation, with Chelsea heaving in their game of catch-up, played perfectly into their hands.
Elimination will not have immediate implications for Benítez, even at a club where nothing should ever be deemed implausible. He is contracted until the end of the season and fully expects to see out the term, encouraged as he apparently was after speaking with Roman Abramovich after Sunday's victory over Arsenal. Chelsea are, after all, well ensconced in the top four and even aspiring to catch Manchester City in third rather than fretting too much about fifth-placed Everton, seven points beneath them. Yet, if the Spaniard did really retain hopes of securing this position on a longer-term basis, then his case has suffered.
He was supposed to curtail all the near-misses, the tone having been set when the Community Shield and European Super Cup were surrendered under Roberto Di Matteo in the autumn. They had felt like unwelcome distractions at the time but there was disappointment from above that silverware had been so casually passed up. The Club World Cup was lost on Benítez's watch and the Premier League title has long since been exposed as a pipe dream. This loss has left the defence of the FA Cup, which will continue at Brentford on Sunday, and the Europa League – a competition Chelsea hoped they would always avoid – as their only routes to silverware.
What was disappointing here was the relatively lacklustre opening, a failure to find reward when in the ascendancy before the interval and some rather predictable substitutions by the end. Chelsea dominated both of these matches in terms of chances created but failed to score and the £50m record signing, Fernando Torres, sat out most of this occasion on the bench. When Di Matteo dropped the Spaniard in Turin this season, it felt like an invitation for a sacking. These days, with Demba Ba generally a more threatening presence, there is more acceptance at such selections, even if Torres may be angered by life on the sidelines.
The reality is that, for all the statistics Benítez can point to as grounds for optimism, there is still something lacking in this Chelsea team. Perhaps that is inevitable in a squad that is undoubtedly in transition. Maybe, had John Terry been fit for both legs, the lineup might have enjoyed that strength of character and unswerving spirit to prevail.
That is what they called upon against Napoli in that second leg last season, and against Barcelona and Bayern Munich in subsequent rounds. Instead, they ended up flattering to deceive at home and away, missing too many chances before frustration properly gripped.
They ended up running aground on stubborn defence here. Benítez had suggested on the eve of this game that "a lot of doors can be opened" if his interim stewardship yielded the trophies this club demand. This felt like one being slammed firmly shut in his face.
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