Carlo Ancelotti had stood lonely in his technical area as the taunt was picked up by the majority crammed into this arena, the cruel chorus of "You're getting sacked in the morning" echoing into the night sky. There was a helplessness about the Italian. This tie had already veered out of his control and with it his side's only chance of securing silverware this season. By the end he was hunched in his disappointment as he shuffled towards the tunnel, exiting stage left from a theatre in which he had previously flourished.

There is the potential for the last six weeks of this campaign to be agonising for Ancelotti. The manager himself admitted after this elimination that his future at the club is at the whim of the owner, Roman Abramovich. That, in itself, represents no radical change of policy. Four managers have been dismissed by the Russian in his eight years at the club, with each dispatched ruthlessly. But until there is public backing issued from the very top of this club, rather than shady suggestions that the manager's position will be "reviewed" in May, the run-in will be dominated by rumours of the possible arrival of Guus Hiddink, Marco van Basten, Frank Rijkaard, even José Mourinho, to fill his shoes.

Those last seven league games must still yield a top-four finish, the bare minimum expected of any Chelsea manager, though recovering from this crippling disappointment will hardly be easy. "We need to move on quickly," said Ancelotti. "We are out of the Champions League and this is not good for us. We are disappointed but this is football. We have to be able to look forward. Above all we have other games to play and win, if possible, because we all want to play in the Champions League next season."

There was an irony that the Italian should be forced to endure this here. Ancelotti used to cherish visits to this arena, the scene of his Milan team's European Cup success over Juventus in 2003, when a corner of south Manchester was transformed into little Italy for one night only. Even last year, when Chelsea had been seeking to regain the Premier League title after four years, it was here that their defining victory was achieved. United were beaten, their challenge broken. This is a stage upon which Ancelotti had tasted so much triumph.

Yet, his mood anchored in defeat, those memories will already be fading. The visiting manager looked unnerved at times on Tuesday night, his frustration clear that his "special" tactical gamble – a switch from 4-4-2 to 4-3-2-1 – had not produced the goal the away team's initial assuredness had suggested would be theirs. Half-chances were missed, Frank Lampard and Fernando Torres fluffing their lines. By the interval Chelsea trailed and the manager, unnerved, had already conceded that his pre-match tactics had been flawed.

Torres, as ever, was the focus of the frustration. Ancelotti had been at pains last week to say he was under no pressure from the hierarchy to select the £50m British record signing from the start, and reiterated as much after this occasion. Yet his inclusion and the omission of Didier Drogba – even with the Ivorian's poor scoring record of one goal in his previous 13 matches – stood out as startling and rather unconvincing. The post-match admission that the selection may have been a mistake betrayed his doubts. "I wanted to put more pressure in front," he added. "But at half-time we needed to score. Didier was fresh and could use his power in front, so I took off Fernando."

It all felt so deeply unsatisfactory. Ancelotti will curse his inability to squeeze a single goal from the Spain striker in 693 minutes as a Chelsea player but this club spent a vast amount on a player whose form had been erratic. It has rather stagnated since. "We have to believe in him," he said. "We have to wait until he improves." Torres will be a Chelsea player next season, when the team could potentially be constructed around him. Whether Ancelotti is there to oversee his recovery remains in doubt.

In the end the manager enjoyed barely 60 seconds of hope here – the time it took between Drogba's equaliser and Park Ji-sung's winner – before Chelsea's chances were extinguished. This season's unexpected toils should not be laid upon him alone.

This had been a team in need of regeneration, a process that began last summer with the release of a quintet of senior players and the arrival of Ramires and continued with the £73m spent on Torres and David Luiz in the new year.

There will be more trimming to come, with occasions such as this – not to mention the club's deficit in the title defence – illustrating the time has come for change. José Bosingwa and Paulo Ferreira, maybe Florent Malouda and Yuri Zhirkov, and perhaps even Drogba and Nicolas Anelka – both of whom will be entering the final 12 months of their deals – could in effect be rendered available. That would have felt unthinkable a year ago but so would the possible departure of a double-winning manager.

Now those realities may be closing in upon Chelsea.