It is anybody's guess as to what tactics Manchester United manager Sir Alex Ferguson will use on Sunday when his side takes on Manchester City at Old Trafford. Prior to this match, it could be argued that United have played five 'big matches' so far this season.

In their 3-0 victory over Tottenham Hotspur and 8-2 thrashing of Arsenal FC -- when both opponents were reeling from transfer window drama -- Fergie kept his foot full throttle on the pedal at Old Trafford and overwhelmed both sides with a fast and fluid 4-4-2 attack. Similar, but somewhat different, tactics were used during United's 3-1 victory over Chelsea FC at Old Trafford. However, the tie versus Andre Villas-Boas' side displayed some vulnerability in United's defense as the Blues created numerous dangerous goal-scoring chances. In a Champions League clash away to Benfica, Fergie used an extra player in the midfield -- the result being a slow and static attack. During last weekend's battle at Anfield -- where United have struggled in recent seasons versus rival Liverpool FC -- Fergie's conservative 4-5-1 did well to limit the opposition's goal-scoring chances, but it's functionality failed to create many for his own side.

Manchester City

City likely present the most formidable test for United thus far this season. They have scored an impressive 27 goals in 8 league matches (3.38/match) while only conceding 6 (0.75/match). The "noisy neigbours" have a deep squad and it is hard to say for certain who will they start on Sunday during the derby.

Under manager Roberto Mancini, City have been well-organized defensively but they have shown more adventure in attack this season. Ahead of their back four, they generally use two deep-lying midfielders -- one true holding player such as Nigel De Jong and another like Yaya Toure or James Milner that has more freedom to get forward with late-arriving runs.

Advanced ahead of the two deep-lying central players is usually a withdrawn forward like Sergio Aguero or an advanced attacking-midfielder like Toure. Their wide players -- David Silva and Samir Nasri -- tend to come inward into the space between the lines so that they can pick up the ball in dangerous areas and provide incisive passes in attack. These players tend to be City's creative force in the attacking third and suppliers for their dangerous finishers.

These wide players coming inside tend to make City narrow in attack -- even more so if both Nasri and Silva are deployed together at the same time. If Adam Johnson is used by City, he can help to provide width. But even he tends to cut in diagonally onto his stronger left-foot when he is on the right flank. If proper width isn't provided by marauding full-backs making overlapping runs, then this can make City predictable in attack. They can be bottled up if the opposition deploy natural foils -- a true holding-midfielder or double pivots -- something United has tended not to do recently. Considering this threat by City, how might Fergie respond on Sunday?

Manchester United

As mentioned previously, Fergie tended to use a fluid and interchangeable 4-4-2 in the early portion of the season-- a shape that has made United free-flowing in attack but vulnerable between the lines of their midfield and defense. Perhaps it is this vulnerability that convinced Fergie to use an extra man in the midfield in the away ties to Benfica and Liverpool. Last season during the run-in, United used a 4-4-1-1 shape that provided a bit more balance.

* fast & fluid 4-4-2

In the early portion of the season, United used a 'fast and fluid' 4-4-2 shape that terrorized the English Premier League. Up front, both Rooney and Welbeck dropped deep -- in 'false-nine' type of roles -- and linked play with the midfield. The wide players -- Nani and Ashley Young -- both were able to either go down the touchline and whip in crosses or cut inside to play quick one-touch football with the two forwards. Anderson and Tom Cleverley worked well together -- one would stay back when the other surged forward -- and helped the attack with well-timed late-arriving runs into the box. As a whole, the attack was free-flowing, fast, and interchangeable. The only vulnerability was when United were not compact enough between the midfield and back four -- this was the genesis of the high number of shots-on-goal that United were conceding. This shape did work well versus City in the Community Shield but it is one that could still make United vulnerable to City's attack on Sunday.

* 4-4-1-1 from last's season's run-in

The main attacking feature from this shape was the use of Javier Hernandez (Chicharito) as a lone striker. He sat on the back shoulder of the opposition's last defender. His intelligent movement between the channels and threat of his pace stretched the defense and in turn, this created more space for Wayne Rooney to operate in underneath. In this space between the lines, Rooney was a creative force -- he was essentially a number ten that created chances for both others and himself. On the left side of attack -- where Rooney often drifted into as well -- the attack was somewhat fluid and interchangeable. Park Ji-sung from a narrow left-sided role, often came inside while Ryan Giggs was free to roam forward or to the left. On the right flank, Antonio Valencia stretched the attack with direct play down the right touchline. The Ecuadorian winger was arguably in the form of his life last Spring and he was difficult to stop one-on-one. Michael Carrick provided balance in his deep-lying playmaking role -- he dictated the tempo from deep while helping to provide cover against the counter-attack.

* 4-3-3/4-5-1 hybrid shape

Using an extra man in the central-midfield is a tactic that Fergie has done frequently in recent years for what some call 'big matches.' This generally means difficult away ties in Europe or tough domestic matches versus the likes of Chelsea, Liverpool, or Arsenal. When United had the trio of Rooney, Cristiano Ronaldo, and Carlos Tevez as the three in attack, they were devastating on the counter. When Fergie wanted to deploy Park as a wide forward or as the most advanced central-midfiedler -- so that the Korean could nullify a deep-lying threat on the opposition -- he complimented the attack well. These players were versatile in their attacking ability and in combination with their intelligent movement, United were an interchangeable force on the counter. This shape has been used less in the past year -- likely because the Reds have looked stagnant at times with their current attackers. Theoretically though, some of United's current attackers -- the likes of Rooney, Nani, Young, Welbeck, and Park -- provide similar versatility and each could potentially thrive still in a 4-3-3/4-5-1. In additon, this shape helps provide a sound shape versus a formidable attack.

What shape will United use against City?

I don't know. But with United playing at home, it's possible that Fergie will be less conservative than he was during this season's away matches at Benfica and at Liverpool. With Cleverley likely not fit nor sharp enough for selection, will some sort of mix of 'fast and fluid 4-4-2' and 4-4-1-1 be used? Will Darren Fletcher or Michael Carrick be used alongside Anderson in a deeper role to provide more cover against City's attack? Will Park be deployed on one side -- as he often is for 'big matches' -- while the attacking creativity of Nani is used on the other side? Will Chicharito start alongside Rooney to resume their unique partnership or will the youngster Welbeck get the start? Or will Fergie spring a surprise and use tactics that resemble nothing that has been discussed (certainly possible)? Sunday should be fascinating encounter for a number of reasons -- tactics could be one.

* full match preview: Manchester United vs Manchester City