It is not quite a novel experience for Jose Mourinho, but it is close. The 779th game of his managerial career will be only the second when he has to occupy the visitors' dugout at Stamford Bridge, the ground where the cult of the Special One has often been at its strongest.
Mourinho can seem a pantomime villain at other stadia but, even during Chelsea's disastrous start to last season, he remained adored in this corner of west London.
So tomorrow should be a strange experience for him. Chelsea's greatest manager will stand in Chelsea's way. When he last did so, many supporters applauded him, a few abused him and Mourinho's defensively sound game plan helped secure a 1-0 win against an Italian manager. For Carlo Ancelotti, defeated by Mourinho's Inter in 2010, do we read Antonio Conte now?
Mourinho would surely settle for a repeat. He began this week with a reminder of his capabilities as a nullifier. Ignore Thursday's 4-1 rout of Fenerbahce: Monday's 0-0 draw at Liverpool was a sign that Mourinho still values pragmatism over popularity, efficiency over entertainment.
He can be an expert analyst of opponents, whether to capitalise on their weaknesses or negate their strengths, even without the inside knowledge he possesses of Chelsea.
The only complication is that, in their last two games, the Blues have signified a break with the Mourinho era. They have started to look like a Conte team. They have adopted a back-three, a ploy the Portuguese invariably eschews.
It renders the tactical battle more fascinating. Despite his brace as a central midfielder against Fenerbahce, Mourinho will surely use Paul Pogba as a No. 10, deploying two specialist defensive presences to track Eden Hazard and Willian, Conte's inside-forwards in his 3-4-2-1 formation.
He will probably target Victor Moses, the winger who has impressed in two games as a makeshift wing-back, but has scarcely been tested defensively. Mourinho could put Marcus Rashford up against him.
There are strategic considerations and human elements. After his final match as Chelsea manager in December, Mourinho accused his charges of betraying him.
Sporting director Michael Emenalo referred to a "palpable discord" between players and manager. The champions turned underachievers, the men who were criticised by him and seemed to fall out with him, now form the core of Conte's team.
Diego Costa and Hazard became symbols of Chelsea's rise and fall under Mourinho. Each is under the spotlight.
The search is on, for evidence of any particular determination to defeat a former mentor, for signs of form that would suggest Conte is getting more from them than Mourinho did or for failings in their game their old manager can expose.
There is intrigue and there are clear consequences. A loser should find themselves a long way behind the league leaders, their title prospects dented already.
CHELSEA V MANCHESTER UNITED
Singtel TV Ch103 & StarHub Ch228, tomorrow, 11pm