This Sunday, Old Trafford will host the Premier League's top team and a high-profile side gasping for air after an underwhelming start to the season.
The latter is eight points behind the former, and the club's fans are publicly questioning its manager's fitness for the job.
As Andrew Mangan wrote for ESPN FC, Arsenal have nothing to fear when they return to Old Trafford—a Theater of Disappointment in recent years—on the back of two consecutive victories against arguably the two best opponents they have faced this year.
Despite injuries to such excellent players as Lukas Podolski, Alex Oxlade-Chamberlain and Theo Walcott, Arsene Wenger has been able to put together exceptionally well-rounded teams that can win in either swashbuckling style or by grinding out close results.
As United know, that combination is a defining characteristic of all title-winning teams.
Meanwhile, the Red Devils have lost the bite they had under the management of Sir Alex Ferguson. Old Trafford is no longer the impenetrable fortress it has been for much of the last quarter-century.
Wenger's men have the mental advantage over their rivals, but the manager still faces some difficult tactical and practical choices when he submits his team sheet on Sunday.
It's not that tough for him, though. He's almost guaranteed to stick with the same formula that has been so efficient against Liverpool and Borussia Dortmund.
The back five is guaranteed to be exactly the same it has been for almost the entire season, barring an unforeseeable pregame injury.
Wojciech Szczesny delivered his best performance of a quietly excellent season against Dortmund, as he continues to brush off competition from Arsenal's other two goalkeepers:
Net transfer spend from 2000-2013: Man Utd—£242.8m, Arsenal—£83.3m (as per @sportingintel)— Bleacher Report UK (@br_uk) November 8, 2013
He will see Bacary Sagna, Per Mertesacker, Laurent Koscielny and Kieran Gibbs ahead of him. That quartet's composure against a relentless (and better) Dortmund team allowed Arsenal to keep a clean sheet and skate by on Aaron Ramsey's goal.
Whereas in recent years Arsenal's defense would have crumbled in similar situations, every man did his part to secure his area of the pitch. As a result, clinical teams like Dortmund or Manchester United no longer give Arsenal fans heart attacks every time they come forward.
Wenger faces a much more difficult choice in midfield.
Mathieu Flamini's return gives him an interesting problem: Should he stack the midfield with disciplined enforcers or attempt to opt for a more forward-thinking, open approach?
The answer is not quite clear. Mikel Arteta will surely not be dropped, so if Flamini plays, it will be alongside the Spaniard. The two formed quite a solid partnership before Flamini banjaxed himself twice, but make for a much more conservative team.
However, caution is justified here. This is still Manchester United, after all, and the Red Devils are but three points away from second place.
United are stocked with attacking talent, and stacking the midfield with players who can settle things down and add a defensive edge is wise.
So expect to see Arteta and Flamini partnering once more at the back of a 4-2-3-1 formation.
But Wenger then must drop one of Tomas Rosicky, Santi Cazorla, Mesut Ozil or Aaron Ramsey—a selection dilemma if there ever was one.
Despite Ozil's relatively lackluster play recently, his ability to spontaneously produce brilliant moments necessitates his inclusion. Aaron Ramsey, one of the most in-form footballers on the planet, is even less likely to be dropped.
It seems odd to say, but Santi Cazorla might well be dropped for this match. He was typically excellent against Dortmund, but Rosicky turned in a virtuoso performance at both ends of the pitch.
The Czech's work rate was incredible, especially considering he is 33 years old. Perhaps his efforts have fatigued him and Wenger's decision will be made for him but it is impossible to justify dropping a man whose relentless pressing and energy on and off the ball spurred Arsenal against a superior opponent.
Such are the pains of having the best and deepest midfield in the Premier League.
But there is absolutely no question, as ever, about who will spearhead the attack.
It will be Olivier Giroud of course. It's one of Wenger's easiest decisions, for his blend of brawn and guile is special and gives Arsenal a dynamic, physical attacking threat that cannot be obtained from anyone else in the team.
If he plays according to his ability, so will the Gunners' attack. And that will be reflected on the scoreline.