Antonio Conte’s homecoming was not supposed to descend into a humiliation.

He must have privately relished bringing his English champions, such a well-drilled outfit last season, back to Italy in the hope they would impose themselves in an arena where, on his last visit, he had been overseeing the Azzurri. Yet everything about this return to Rome was nightmarish, with Chelsea shredded at the back and profligate up front. Leadership of this section has been lost but, more significantly, this team feels damaged. They have rarely performed so chaotically.

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The only consolation, and it will feel considerable in the cold light of day, was Atlético Madrid’s failure to overcome Qarabag’s 10 men in Spain, which means a win in Baku at the end of November will still secure progress into the knockout phase. Yet, rather than fret over the machinations of Group C, Conte’s priority must be recovering confidence for Manchester United’s visit to Stamford Bridge on Sunday. Defend as poorly as they did against Roma and, even if José Mourinho is thinking safety first, the visitors will sense plunder.

Plenty will point to the summer sale of Nemanja Matic to United as reason for Chelsea’s sudden vulnerability. More pressing at present, of course, is N’Golo Kanté’s absence. Conte and his medical staff had deemed it would be “stupid to risk” selecting the Frenchman at the Stadio Olimpico with his recovery from hamstring trouble still not properly complete. They missed his instincts in defensive midfield yet again here – this team have conceded 11 goals in the six matches he has missed, with only one clean sheet en route – with too many players across Chelsea’s midfield and forward line carrying wear or aching limbs to compensate. Even so, their rearguard should have offered more resistance than this.

Play Video 0:35 Conte furious with 'really, really bad' Chelsea after Roma defeat – video

They were overwhelmed, punctured after 38 seconds and tormented thereafter by Edin Dzeko’s brawn and clever movement, and the slippery pace of Diego Perotti and Stephan El Shaarawy on the counter. Conte had tried to rejig things, moving Gary Cahill to the right of his back three, then hauling off his captain before the hour-mark and even employing Pedro as a right wing-back, but fragility persisted. Perotti’s third was skimmed low from distance after Cesc Fàbregas surrendered the ball and Pedro had merely dangled a leg in an attempt to block the forward’s burst, yet it was an opportunity moments later that truly summed up this mess of a performance.

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Another counterattack had Chelsea exposed with all three centre-halves drawn to Dzeko in possession as he approached the edge of the penalty area. The Bosnian merely checked back, with Antonio Rüdiger, David Luiz and César Azpilicueta in a neat line pointing at goal but all horribly off balance, and slid a diagonal pass across the box to the unmarked Perotti. The forward skied his shot over the bar, but the visitors had been split apart.

Facebook Twitter Pinterest Stephan El Shaarawy takes advantage of Chelsea’s defensive indecision to score Roma’s second goal. Photograph: Ettore Ferrari/AP

It would take Thibaut Courtois’ fine instinctive save from Kostas Manolas to avoid a four-goal drubbing. Regardless, Chelsea departed Italy chastened as the first English team beaten in this season’s competition, and with much to ponder before the weekend.

They were never comfortable, having been breached with the game in its infancy, the back-line perhaps still adjusting as Aleksandar Kolarov flung over a cross from the left. Dzeko, in between David Luiz and Rüdiger, improvised a lay-off via head and shoulder with the ball dropping in to space just outside the area, territory that might normally be patrolled by Kanté. While Marcos Alonso dawdled, El Shaarawy sprinted through on the wing-back’s inside and dispatched a first-time shot with the outside of his right foot that careered beyond Courtois. Roma have never registered a quicker goal in this competition.

Conte had relished coaxing the best from El Shaarawy with the national team, but here he was a rival running riot. The forward should have added a second just after the half-hour mark, bursting on to another Dzeko pass after David Luiz had surrendered the ball carelessly. Courtois blocked that attempt with his feet, but the respite was brief. Within a minute, Radja Nainggolan centred from the left and Rüdiger, unaware that El Shaarawy had a run on Azpilicueta’s inside at his back, chose not to intercept. The Italy forward could not believe his luck and simply guided the ball beyond a static Courtois.

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What made Chelsea’s frustration all the more acute was that, as an attacking force, they had actually posed a threat in that opening period.

Alisson had denied Eden Hazard three times before the break, as well as turning away Alonso’s curled attempt. More wasteful for the visitors were the misses from Álvaro Morata, an anxious attempt in front of goal after Pedro had blocked a clearance, and Tiémoué Bakayoko planting a free header wide from Fàbregas’s corner, where the Brazilian goalkeeper would have stood no chance.

Yet that failure to register knocked the stuffing from their display, with everything that followed “a disappointment” for the crestfallen Conte. Time is limited in which to conjure a recovery. This season is already taking its toll.