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The role of the controlling midfielder in a 4-3-3 consists of two parts; that of the team being in possession, and that of when the team is defending.
In possession, the controller must always be available to receive the ball off a team mate.
No matter if the goalkeeper has the ball—and the midfielder drops deep, outside the penalty area, to receive and dictate play from his own goal area—or the false centre forward does, the man in the middle for Liverpool needs to be aware, in space and ready to receive.
When he gets the ball he needs to know already where his nearest team mates will be, who will be making a run into different areas of the pitch and exactly how capable he is himself of finding each potential recipient without risk of losing the ball.
The player in question needs to do this not just by looking up and using his eyes, but tactically already be aware of all these factors, in order to keep the tempo of the play going, provide a quick outlet and get the team building a new attack.
In form and with the team playing well, he might have to do this anywhere between 50 and 100 times per game.
Out of possession, the controller needs to know which midfielders from the opposition team are due to make forward runs, decide if he himself needs to track or block them off or if a fellow Red should do the job, and protect his entire back four.
This latter role might consist of remaining central, dropping into the defence itself or covering the full-backs who are expected to play and press high up the pitch.
All in all it is a hugely demanding role requiring great concentration, stamina, consistency and discipline.
In Lucas Leiva the Reds have someone capable of doing all of that.
Joe Allen, Liverpool's newest centre midfielder, has expressed his own more secure state of mind when Lucas is on the pitch:
His return, with the steel and quality he brings, is only going to help the team going forward. It's a very important role. If you look at the top teams, they all utilise that position and have a quality player there. Lucas is vital for the way we play. With him back playing, I'm sure we'll get the benefits of that in terms of points and our position in the table. I had that security of knowing that Lucas was there. It gives you the chance to express yourself further up the pitch, and try to get involved in creating and scoring goals.
There might be a time in the future when the role has additional demands; the odd foray forward, a more expansive or creative outlook to passing or driving shots in from range. When that happens, maybe Lucas is the player to build back up the attacking side of his game, or maybe not. Regardless, Liverpool are some distance from that time at present.
Right now though he is the perfect holding midfielder for Brendan Rodgers and for the team, and Liverpool are a much better side when he is in the starting 11.
It's fitting that Lucas himself should have the last word: