When Manchester United play Chelsea, you don't usually need to add much of an edge. Since Chelsea won their first Premier League title in 2005, these two have been champions 10 times in 13 seasons: only the money of Manchester City and the miracle of Leicester have kept it from being a clean sweep.
But of course, there is an edge this time. Feuds between Jose Mourinho and other managers can have a pantomime feel, like boxers who pretend to hate each other in the name of hype, but there is most certainly something extra this time: Mourinho and Antonio Conte genuinely do not like each other.
Half an eye will be on the touchline but the important stuff will be on the pitch. So how do these rivals measure up?
In most other comparisons, Thibaut Courtois would be far and away ahead of his opponent. There are only a few keepers in Europe who can really claim to be on his level: Manuel Neuer, Gianluigi Buffon, Jan Oblak, possibly Gianluigi Donnarumma and also of course, the man that he'll be facing on Sunday, David de Gea.
United's man between the posts has been a constant since his arrival in 2011, which in many ways is just as well considering the various forms of chaos that have unfolded in front of him in that time: United have arguably depended on him more than any other single player. His consistency has not been matched by Courtois, who like many of his teammates is not quite the force he was last season.
To a point, the answer to this question depends on fitness. United have half of a reliable back four -- Antonio Valencia and Eric Bailly being two of the more solid defenders in the Premier League -- but then there's a smorgasbord of relative mediocrity to fill the other two spots. Does it matter a great deal whether Phil Jones or Chris Smalling or Victor Lindelof play? Probably not. Luke Shaw probably deserves a more consistent run but equally Ashley Young, odd as it may seem, rarely gets much wrong.
Chelsea's back three looks more solid. Cesar Azpilicueta might be the most dependable defender in the country, Andreas Christensen is a rising star and one of Antonio Rudiger or Gary Cahill are perfectly competent. And yet oddly United have a better defensive record in the league. That's probably down to factors beyond simply the defensive personnel, though.
The big question for Sunday will be whether Mourinho selects Paul Pogba. His omission for the Champions League game against Sevilla was one of those things that was and wasn't surprising given that he's a player who can make the team sing on his day but who can be maddeningly anonymous on others. The rest of United's midfield is a problem, too: Nemanja Matic's form has fallen away, Ander Herrera isn't the most consistent (he also might miss out through injury) and Scott McTominay is too young.
Chelsea's central pair will almost certainly be as it was against Barcelona, N'Golo Kante and Cesc Fabregas providing a solid mixture of creativity and endeavour. They'll be flanked, of course, by the super-reliable Victor Moses and Marcos Alonso, who perhaps surprisingly has been one of their better players this season. Neither midfield is perfect, but Chelsea's probably provides fewer questions.
Chelsea have the best individual forward in both teams. In fact, Eden Hazard is the best player, full-stop, on either team. But judging the two attacking units is a question that requires slightly more thought. For all he looks unconvincing against the best teams, Romelu Lukaku seems a more reliable source of goals than Alvaro Morata or Olivier Giroud, particularly given the former's recent fitness problems.
And while Pedro and Willian have been in fine form, United simply have more threatening options available to them. Alexis Sanchez, Marcus Rashford, Anthony Martial, Jesse Lingard and Juan Mata are useful: Mourinho's problem is finding the best way to fit as many of them into the team as possible rather than a lack of choice. When he gets that right, United should (in theory) be a fearsome attacking force.
It's clear which manager is more secure in his job: much to the chagrin of any United fan who enjoys watching entertaining football, Mourinho recently signed a new contract while Conte has reportedly been a bad result or two away from the sack in the past few months. But the question of which manager is actually doing a better job this season is more difficult.
Going purely on the league table, Mourinho would seem to have the edge. But he has been able to assemble a squad broadly to his specifications and is still producing football so grindingly tedious as to make one weep. Conte has been forced to cope with the internal machinations of a complicated club that has seemingly bought players he has little interest in using, but is still managing to compete.
Ultimately this game is more important for Chelsea. United will still be in a strong position to finish in the top four whatever the result, but defeat for Chelsea would probably put them out of the Champions League places and with more of a scrap on their hands of getting there. Should Chelsea win, they would go level on points with their opponents.
Both teams go into the game on the back of draws in their Champions League games but there's not really any contest in whose was the better result. Chelsea might feel slightly disappointed to have only drawn 1-1 with Barcelona, but United were lucky not to be beaten in Seville. Will that have an impact on how either side performs at Old Trafford?
Overall prediction: Manchester United 1-1 Chelsea