Among European Cup finals, FA Cup finals and Premier League deciders, we've witnessed some crucial fixtures between Chelsea and Manchester United in recent years. Yet the entire feel of this contest has altered recently – partly because Manchester City's emergence as title contenders has rendered it slightly less important, but also because of the strategies of the two sides.
For much of the past decade, this was generally a fierce, scrappy and unattractive match. Chelsea offered great power – the sheer physique of midfielders such as Frank Lampard, Michael Ballack, Michael Essien and Claude Makelele was an intimidating prospect, and Sir Alex Ferguson generally responded by attempting to shut down the game. It was a fixture for the likes of Park Ji-Sung, Owen Hargreaves, Darren Fletcher and John O'Shea – unspectacular but hard-working players who could be relied upon to fight. Their versatility also was a handy tactical weapon.
Yet three of those players have left, and even Fletcher must reinvent himself, robbed of his famous energy by serious illness. So United don't have that same battling quality. But against a more technical Chelsea side, it shouldn't be a huge problem. "It is a different Chelsea side now," acknowledges Fletcher. "It used to be a big strong physical side, playing against Michael Ballack, Claude Makelele and Frank Lampard in midfield and Didier Drogba up front, whereas now you are facing more like Barcelona players, the small intricate players who get in the pockets behind you and they play killer passes."
Besides, Ferguson has changed strategy. Rather than selecting combative players, he has attempted to control the tempo. United's 1-0 European Cup victory at Stamford Bridge in 2010-11 was a fine example – the central midfield combination of Ryan Giggs and Michael Carrick's assured passing created a patient, cautious game. Wayne Rooney netted the only goal after a fabulous crossfield pass from Carrick to Giggs.
When Chelsea had beaten United in the Premier League a few weeks beforehand, there was the same pattern, but a different result. United dominated and went ahead when the game was played at walking pace, then Chelsea fought back, upping the tempo and chucking on Didier Drogba to make their play more vertical. Carlo Ancelotti's side won 2-1.
Last season's matches were incredibly frantic. United won 3-1 at Old Trafford despite a good Chelsea performance in Andre Villas-Boas' first big test as a Premier League coach – Fernando Torres' open-goal miss ruined Chelsea's hopes of a comeback, but it wouldn't have been any more ludicrous than United's fightback from 3-0 down at Stamford Bridge to draw 3-3 earlier this year. Ten goals in two matches – and there should be more this weekend.
Both Chelsea and United are currently top-heavy, significantly stronger going forward than defensively. Summer signings ensured that: Chelsea splashed out on Oscar, Marko Marin, Eden Hazard and Victor Moses, while United brought in Shinji Kagawa and Robin van Persie. "There is no doubt our attacking play is the best part of the team at the moment," said Ferguson after last weekend's comeback against Stoke. "Our forwards got us out of trouble again because our defending has been slack." This weekend, he will focus on attack.
In terms of selection, Roberto Di Matteo seems unusually constrained by a lack of options. He essentially has two formations this season – either he plays Oscar, Hazard and Mata behind Torres, with two central midfielders behind, or he can use Ramires in the attacking trio, as a more cautious approach. The latter strategy relies upon Lampard playing alongside Jon Obi Mikel, however – and after Lampard limped off against Shakhtar on Tuesday night, he's a doubt for the weekend. Three playmakers behind Torres seems likely.
In Tuesday's Champions League match, the major contrast between Chelsea and Shakhtar was the familiarity of the respective attacking quartets. The Ukrainian champions looked cohesive while Chelsea remain a work in progress. In possession, it's about individual imagination rather than consistently effective combinations, and without the ball Chelsea are slow to get back into position, particularly in wide areas.
"If we do win the ball, [Chelsea] will leave a lot more spaces than you normally expect," said Fletcher. "Traditionally, they are very solid, have men behind the ball and are hard to beat. However, with all those attacking players, they may give us spaces to exploit."
Knowing that weakness, Fletcher's manager has a formation decision to make – his "revolutionary" diamond, or the more traditional 4-4-2 / 4-4-1-1 system? The former would allow United to pack the centre of the pitch and field an extra forward, with Wayne Rooney at the tip of the diamond, as in the midweek win over Braga. Yet the latter offers more width, and because Chelsea's full backs lack protection, that might be a wise option.
Alternatively, Ferguson could go for a hybrid system. Three years ago in this fixture he played Ryan Giggs in a narrow, deep left-sided position in a 4-3-3, essentially creating a diamond, in combination with Antonio Valencia out on the right and Rooney up front. United lost 1-0, but dominated possession, had more chances, and were unlucky to lose.
On Sunday, Rooney could play behind van Persie, perhaps with Danny Welbeck on the left coming inside and Valencia wide on the right; Ferguson is happy to leave Branislav Ivanovic free, but wants to occupy Ashley Cole. Michael Carrick and Tom Cleverley could play the midfield roles. A lopsided diamond? A misshapen 4-3-3? It doesn't need a label if it does the job.
With Di Matteo lacking options, the ball is in Ferguson's court. He knows how Chelsea will set up – he must consider the best way to exploit their weaknesses. The stage is set for a fascinating tactical battle, and another attack-minded contest.
Michael Cox is a freelance writer for ESPN.com. He runs zonalmarking.net.