Defensive deficiencies and injury problems are threatening to derail Chelsea's season... so could manager Antonio Conte face the sack if they lose to Manchester United?

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The suit is as sharp as ever, the touchline conducting as frenetic as ever, but right now Antonio Conte is not looking like the manager who swept Chelsea to the Premier League title last season.

Chelsea's 3-0 defeat to Roma in the Stadio Olimpico owed much to individual mistakes but was underpinned by architectural faults of Conte's making and the scrutiny that comes with the territory at Stamford Bridge will only increase.

The loss in Italy is by no means terminal to ambitions for qualifying for the last-16 due to Atletico Madrid's failings against Qarabag. Nor are Chelsea drastically out of position in the Premier League table in fourth.

Chelsea's season is threatening to come apart amid injury concerns and defensive problems 

Antonio Conte's side were beat 3-0 in the Champions League by Roma on Tuesday evening 

But in trailing leaders Manchester City by nine points, a successful title defence seems out of reach already, and a third defeat in seven games in all competitions speaks to deeper issues. 

Should Sunday's game against Manchester United go wrong the focus will fall on Conte even more. Sportsmail looks at the problems afflicting his season.

Defensive deficiencies

The goals Chelsea conceded in Rome may have been examples of clinical finishing but for each the backline was breached far too easily. 

The first two were straight-forward balls over the top that should have been gobbled up by a back-three system, yet instead spread confusion totally at odds with Conte's typical organisation.

The third was a case of loose possession and flimsy tackling, while there was also a comedy moment when all three central defenders chased Edin Dzeko like schoolboys, leaving Diego Perotti in space from which he should have scored.

Diego Perotti (above) and Stephan El Shaarawy profited from Chelsea's defensive frailties 

Antonio Rudiger was the most culpable on the night, fatally leaving Radja Nainggolan's hopeful pass to allow Stephan El Shaarawy a second goal, and late on being aerially beaten by Kostas Manolas before Thibaut Courtois came to the rescue with a stunning save.

It was a defensive display symptomatic of a campaign that has slumped in standards from Conte's debut. His side have kept only five clean sheets in 16 games so far (one per 3.2), compared to 19 in 47 last term (one per 2.5).

In the Premier League Chelsea have let in 10 goals in 10 games, one more than Burnley and Newcastle and the same as Southampton. In winning the title they conceded 33 goals in 38 games at a rate of 0.86 goals per game. Something needs fixing.

Selection questions

Last season Conte was able to rely on the same 11 players week after week because of an absence of European football. Training sessions were hard and tactical preparations for each fixture extensive. The Champions League has inevitably disrupted that flow.

Gripes around Conte's rigorous demands have subsequently surfaced – although that is a natural consequence of patchy form – while the Italian is also having his rotation capabilities tested for the first time in England.

Central midfield pair Tiemoue Bakayoko and Cesc Fabregas were overrun against Roma

The clarity that drove Chelsea last season has morphed into confusion, with suspicions arising that Conte does not know his best team. 

On Tuesday night the midfield duo of Cesc Fabregas and Tiemoue Bakayoko was outnumbered and repeatedly overrun by Roma's trio, a predictable conclusion ahead of kick-off. 

That choice was all the more curious given Conte successfully employed a midfield three in the victory at Atletico Madrid, with Pedro sacrificed.

Conte's decision to take off Gary Cahill and put Pedro to right wing-back – from where Roma's third arrived – also struck as odd.

Injury headaches

The hamstring injury suffered by N'Golo Kante while on international duty three weeks ago has undoubtedly impacted Chelsea. 

At his best, the PFA and FWA Player of the Year gives his side the impression an extra man, while in his absence it sometimes seems like they are playing with just 10.

The hamstring injury suffered by France star N'Golo Kante has undoubtedly impacted Chelsea

The calf injury that had kept Danny Drinkwater out until the past week has compounded matters. But now the 27-year-old is back and his former Leicester team-mate Kante is also in contention for Sunday's visit by United having stepped up to full training.

Conte also needs Victor Moses back following his hamstring injury picked up in the 2-1 defeat to Crystal Palace. Cezar Azpilicueta played right wing-back in Rome but does not provide the kind of attacking threat required to make Conte's formation work fully.

More from Morata

Having started the season in spectacular form, Alvaro Morato has now not scored since suffering a thigh injury against Manchester City on September 30. He netted seven in his first seven appearances, including a fine finish against Atletico, but has gone 345 minutes without scoring and even more troubling does not look confident to end that run.

Summer signing Alvaro Morata (centre) has gone 345 minutes without scoring for Chelsea

Against Roma he should have equalised when set up by Pedro in the 25th minute but instead hesitated and scooped his shot well over, looking nothing like the bullish centre-forward of August and September. 

Morata has only completed 90 minutes once since his injury – recording minutes of 35, 90, 61, 5, 79, and 75 – and perhaps he has not full shaken off the problem. His quotes around finding London life stressful and pining for Turin only add to the sense not all is right.

Anxious Abramovich

At nearly every other club, a manager of Conte's achievements would be able to shake off these issues with a pledge that in time the necessary corrections would be made. But Chelsea are not like any other club and a title victory only provides incubation for so long.

Title victory provides job security for only so long at Chelsea under Roman Abramovich

Conte knew this in the summer, hence his loud and consistent agitations for further support in the transfer market. A Champions League campaign would require deeper quality, but a number of his targets failed to materialise for one reason or another. 

First Alex Sandro and Romelu Lukaku, then Alex Oxlade-Chamberlain, and finally Ross Barkley.

Chelsea did commit many millions to other transfers but are not about to allow any manager a complete overhaul. 

The structure is more important than the individual in the dugout and for all Conte's brilliance in wringing a title win from his first campaign, Roman Abramovich remains the boss.