If their men in the middle prove to be masters of their domain, Manchester United will falter.
In an irony probably not lost on either manager, Jose Mourinho and Arsene Wenger have more in common right now than they'd care to admit.
In midfield, there is an embarrassment of riches. Up front, there is the risk of being richly embarrassed.
The Gunners may not be overwhelmed by midfield quality, but they are spoilt for choice compared to their paltry offerings in attack. Chelsea know the feeling.
The two halves of Manchester have divided the best of the Premier League's goal-scoring machines among themselves, leaving both Mourinho and Wenger doing a headless chicken double act in the final days of the transfer market.
The performances against Hull City and Aston Villa underlined Chelsea's shortcomings to their manager. The keys to the EPL kingdom will not be entrusted to Fernando Torres, Demba Ba or Romelo Lukaku. Lukaku remains the best bet in the long-term, but he remains an apprentice.
The sorcerers are huddled together around the centre circle cauldron. Mourinho's magic must be conjured from midfield. Old Trafford is an intimidating fortress, but the hosts' midfield is by no means impregnable. Michael Carrick remains a resolute gatekeeper, but if he can be isolated, the Red Devils' drawbridge can be pulled down.
Just as Mourinho and Wenger obsess over new strikers, United manager David Moyes frets over his threadbare midfield. Many of his rumoured targets have been creative string-pullers; men who specialise between the lines.
Moyes doesn't have enough impudent scamps to pick stubborn locks. Mourinho has more artful dodgers at his disposal than Fagin in Oliver Twist. In congested midfields, you've got to pick a pocket or two. Chelsea could pinch the lot at Old Trafford (and run off with the silverware at the end of the season).
Mourinho's options easily outweigh his rival. Eden Hazard has been earmarked as the side's creative enforcer by his manager and made a nuisance of himself against both Hull and Aston Villa. But, like the flame that burns twice as bright, he burns out by half-time.
His manager will demand a more balanced, disciplined display alongside the increasingly influential Oscar. Like Hazard, he fizzled in the latter stages against Villa but he fizzed early on in his favoured No. 10 role.
If Mourinho does land Wayne Rooney, highly unlikely at this stage, the service he could expect from both Hazard and Oscar would be precisely why he wants to leave.
Ramires or Frank Lampard should be expected to shackle Tom Cleverley and Andre Schuerrle impressed when he came on against Villa. The German has been pencilled in as an integral part of Mourinho's masterplan.
He will feature at Old Trafford. Hazard, Oscar, Ramires, Lampard and Schuerrle are a famous five ready for a boy's own adventure in Manchester. United's midfield can't get close. There's also that guy Juan Mata - remember him? - who was Chelsea's most effective and consistent creator last season.
Like Joe Cole before him, the Spaniard's tendency to improvise and stray from the script already seems to irritate the formulaic Mourinho (Mata's inability to track back certainly bothered his manager against Villa).
But United have no one within their midfield ranks to rival Mata's ingenuity. They spent the British summer fruitlessly pursuing Cesc Fabregas for a reason. Industry is not an issue, but Old Trafford the place is short on inventors.
Chelsea's midfield must flex their muscles, emphasising their side's strengths while simultaneously shutting down their opponents' greatest asset. Keeping the ball should not be a problem. Keeping the ball away from Robin van Persie is a solution.
Ramires, Lampard and perhaps Schurrle will share patrolling duties between the lines, dropping back to cut the umbilical cord between the Dutchman and his midfield. If they suffocate van Persie, United will struggle to breathe.
Moyes could be mischievous. He may call on the man that Mourinho desperately covets. Rooney and van Persie are the riskiest proposition for Chelsea. But the wily Blues boss is playing the magnanimous one; promising not to launch a third bid until after the game.
The inference is clear: No bid this week, no Rooney selection this week. Both clubs, both managers and the man himself know that a higher offer is coming. How could Rooney possibly keep a clear head when all around him are losing theirs?
His body belongs to United, but the soul seems set on Stamford Bridge. Could he realistically be picked?
If Rooney is benched and van Persie is neutered, Old Trafford will host a straight fight between the two midfields. Consider their respective strengths. At 39, Ryan Giggs could start for United. Mata could be on the bench for the Blues. That's the difference.
Between the two dugouts, there is a gulf in midfield depth and quality. If the battleground is contained around the centre circle, Mourinho will head home with the three points.
And Moyes will head straight for the transfer market.
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