Defeat could hasten Conte's seemingly inevitable divorce from Chelsea
Until this week - and Chelsea's latest aberration of many - no English club had suffered a defeat in the Champions League this term.
Chelsea's remarkable success in winning the competition in 2012 was followed by a lengthy famine; the fact that Leicester City went deeper than any of their compatriots last term reflected England's struggles.
That may change this season, particularly as the continental giants show signs of strife, aside from moneybags PSG.
Chelsea are still in a position to qualify for the knock-out stages and all five English sides may yet do so, emphasising the increasing likelihood that this may be the Blues' best chance of landing a big prize as Manchester City's domestic dominance shows little sign of stalling.
The joy of Chelsea's smooth run to the title last season - once they had altered their formation to three at the back against Hull in October, prompting many rivals, even Arsenal, into imitation - seems a distant memory.
So, too, any illusion that the Italian is in charge of affairs. At Chelsea, a manager is never truly in control; or if so, only briefly.
Conte looks like a very unhappy boy and many relationships around the club must be very strained.
He has made constant references to how the club have not adequately recruited and with every dodgy result, his exasperation grows.
Having taken it upon himself to discard the troublesome albeit effective Diego Costa out one door, the unbelievable sale of Nemanja Matic to a title rival left a huge hole in a team which seems to be almost approaching crisis point following the 3-0 midweek reverse to Roma.
Neither Alvaro Morata nor Tiemoue Bakayoko are currently capable of attaining the levels of the duo they replaced.
Morata, a gentle giant, simply doesn't have Costa's presence and that combative ability to occupy and occasionally disrupt an entire back four.
He has never been a leading light before and is now struggling to cope with the demands of being the side's main man in two competitions.
Conte often struggled to combine the challenges of a domestic title race with the higher ambitions of the Champions League during his time at Juventus and this season appears to be no different.
Chelsea are impatient in such matters and are ruthless in dismissing their managers, regardless of their trophy haul.
Conte, who perhaps naively thought that he might assume more responsibility on the back of the title success, is already itching to return to Italy and defeat to Manchester United tomorrow could hasten what seems an inevitable divorce.
Perhaps Jose Mourinho might choose to whisper this reminder in Conte's ear; a different message to that last season when he chided the Italian for being a tad over-exuberant in his celebrations during United's 4-0 trouncing at Stamford Bridge.
Of course, Mourinho was sacked - twice - by Chelsea so there will already be an edge to this fixture. It is in his nature to want to stick it to Chelsea.
His Manchester United are rolling along in the slipstream of their city rivals; they had the luxury of resting players in midweek which will help although his side did retain a strong spine against Benfica.
His self-proclaimed cuteness in tactically out-smarting a Spurs side that had scored freely against Liverpool and Real Madrid will strengthen his determination to retain similar tactics tomorrow.
We may well see an extra defender on the right-hand side in front of Antonio Valencia, perhaps in the guise of the revitalised Ashley Young, considering that duo's effectiveness in limiting the influence of Philippe Coutinho against Liverpool at Anfield.
Mourinho's ability to produce tight games with positive results may provoke yet more arrogance from a man who has started to admonish even his own fans. It is a risky policy indicative of another manager who is perhaps also itching to get away.
You don't have to admire Manchester City or their purchasing power but you can have nothing but admiration for their style of play.
They've averaged three and a half goals per game in the league and their attacking game is at a different level now.
This has been based on a much sturdier defence; Nicolas Otamendi is likely to be the only survivor from the defence that played in City's home clash with Arsenal last term, when the Gunners scored first against a vulnerable rearguard yet were still overwhelmed.
As much as it is obvious how brilliant the forward line has been, or the intricacy of the midfield passing, the effectiveness of the defence has been the key difference.
Once Celtic and Spurs removed Emperor Pep's clothes last season, they struggled and now the challenge is there for teams to find new ways to breach them.
Arsenal surely can't go there in their normal style and try to out-play them in a loose fashion.
They can't afford to be caught with both wing-backs high up the pitch with Aaron Ramsay behind them, vulnerable to the counter.
Arsene Wenger needs his team to stay compact and ensure that there is always protection and organisation against devastating counter-attacks.
A more conservative approach from Granit Xhaka and Ramsay is essential; too often in the past, against the better teams, they have been exposed in central areas and on the counter.
If they are realistically to get back into things, they really need to make a statement.
They haven't won an away game against a leading side since a 2-0 victory over City in January 2015 and have already lost three times on the road this term.
The ability of Mesut Ozil or Alexis Sanchez to produce some magic may be their only hope but my hunch is that City's attacking menace will prove too much for them.