Arsenal's FA Cup replay win over Swansea City showed that Arsene Wenger must continue to deploy a four-man midfield. The Gunners had greater balance and purpose thanks to their quartet in the middle.

Wenger's skilful readjustment of his side, may have been induced by fixture congestion, but he settled on a formula he should keep. Wenger moved Santi Cazorla out of the middle to a position on the left. He also introduced Francis Coquelin alongside Abou Diaby in defensive areas.

These moves were significant, because they allowed Jack Wilshere to act as the creative fulcrum in the middle. With Diaby and Coquelin acting as a two-man buffer, Wilshere was afforded the luxury of spending almost the entire match in the attacking third.

His quick, pass and move style and imperious skill on the ball, mean Wilshere belongs in advanced positions. That's where he can do the most damage and so it proved against Swansea. He routinely outwitted defenders with tricky ball skills and threaded Arsenal's possession together with smart distribution and subtle movement.

Of course as Cazorla has found this season, no one player can carry the creative burden alone. This has been a problem in Arsenal's usual hybrid 4-3-3 formation. Wenger has attempted to dovetail the efforts of Wilshere and Cazorla together in the attacking third.

It hasn't really worked, mostly because Cazorla and Wilshere often get in each other's way. They are vying to control the same areas. This problem was remedied by Cazorla starting out wide against Swansea.

With Cazorla beginning on the left, it meant Wilshere had those central positions primarily to himself. It also meant that Cazorla could link up better with Wilshere by varying his movement from the outside-in. The Spaniard routinely drifted into central positions, to occupy areas just behind the advancing Wilshere. He also showed up on the right, linking with Wilshere's runs.

Cazorla's movement is what Wenger usually expects from his wide players. That's why his best teams have always favoured wide midfielders, rather than true wingers. Lukas Podolski can't offer the same range of movement, because he is by nature, a forward. Cazorla's runs kept the flow and precision of Arsenal's passing consistently high.

Wenger's four-man midfield offered perfect balance. The defensive base was solid, thanks to the extra deep-lying player, Coquelin. That gave more impetus and freedom to Wilshere further forward. He was offered vital support from Cazorla's intelligent lateral movement behind.

The result was an Arsenal team that kept the ball better and played quicker than they have in recent weeks. Yes, they struggled to break down Swansea in the first half. However, it isn't easy to break down a stubborn defensive structure, with as many as nine behind the ball.

The point is Arsenal were able to dominate possession, particularly in the second half. In that second period, the extra man in midfield paid dividends. It also helped when Arsenal were out of possession. The two-pronged attack of Theo Walcott and Olivier Giroud were able to press higher, knowing there was a solid base behind them. That meant Swansea were routinely harassed into surrendering possession.

Contrast these benefits with Arsenal's tired-looking 4-3-3/4-5-1 mix. That formation requires greater width. This isolates the central striker, which can render that player, particularly if it's Theo Walcott, irrelevant. It also puts more pressure on a midfield that has only three. That formation simply leaves Arsenal too stretched because of the lack of cohesion it places on the midfield.

With just one defensive shield, Wilshere is forced to play the dreaded, "box-to-box" role. That increases the physical demands on him and takes him away from the areas where he does the most damage. A three-man midfield also leaves Arsenal short one technically assured ball player. This hinders their ability to maintain possession and create combinations of intricate passing and fluid movement.

Wenger simply must heed last night's lessons and continue to play with four true midfielders.