There have been only three genuinely significant recent changes in football's regulations: the liberalisation of the offside law, goalkeepers being banned from handling backpasses and the increasingly strict manner in which tackling is judged. The other tactical developments are about improved organisation, improved physical conditioning and, perhaps the most significant feature, simply doing whatever's trendy or what the most successful sides happen to be doing.
The fall -- and slight rise -- of the box-to-box midfielder owes much to that final factor. Back in the days of the 4-4-2 and relatively slow football (compared to the pace of the modern game), it was entirely permissible for a manager to field two box-to-box players in tandem who would work up and down the pitch. Contributing heavily to both defending and attacking was, after all, generally considered the point of the midfield.
Yet just a few years ago, the box-to-box midfielder appeared dead. Matches were being played at much higher intensity. The increasing emphasis on speed meant it simply wasn't possible to relentlessly dart between the two penalty areas. When combined with the emphasis on passers in midfield, potential box-to-box midfielders were soon cast aside -- or, rather, turned into different players.
Take Steven Gerrard and Frank Lampard, for example, two footballers who grew up as box-to-box midfielders in the flawed English tradition of star players attempting to do everything. Lampard and Gerrard were pushed forward by their clubs into the most advanced midfield role. This was why they never truly worked together for England, but that is a separate story; the point here is that both were natural No. 8s yet were deployed as something closer to a No. 10. Gerrard's best form came in the same midfield as Javier Mascherano, a defensive battler, and Xabi Alonso, a pure passer.
That pattern was broadly replicated around Europe, with box-to-box midfielders barely featuring. In his profile of Oscar this week, Tim Vickery explains the "separation of functions" in the Brazilian midfield since 1982; a similar thing occurred in European football.
During this time, the qualities offered by box-to-box midfielders were effectively outsourced to the full-backs. From being solid defenders who could occasionally scamper forward and swing in a cross, full-backs suddenly became the most energetic players. For example, Dani Alves provided the verticality in a Barcelona side with three pure passers (Xavi, Andres Iniesta and Sergio Busquets) in the centre of the pitch. But in years gone by, he might have been fielded alongside Busquets and told to get up and down. In fact, that's the role he sometimes played for Brazil under Dunga when he fell behind Maicon in the pecking order for the right-back slot.
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Arguably, however, there's been another shift. Teams are no longer quite so determined to field pure passers in the centre of the pitch, and the recent success of sides like Juventus, Borussia Dortmund, Atletico Madrid and Bayern (under Jupp Heynckes) has demonstrated the value of extremely energetic central midfielders.
There has also been a slight repopularisation of the 4-4-2, which inevitably means the two central midfielders cover more ground. An interesting case study last season was Manchester City, which theoretically started the campaign with two box-to-box midfielders in Yaya Toure and Fernandinho. But while Toure has the all-round midfield qualities to play anywhere in midfield, it's rare to see him genuinely playing a box-to-box role. He storms forward from deep but often takes an eternity to get back into his defensive position.
In the opening weeks of the season, this left Fernandinho exposed as the Brazilian attempted to play his own box-to-box game, which he had become renowned for at Shakhtar Donetsk. By the second half of the campaign, City had settled into a more cautious midfield arrangement, with Fernandinho's role closer to that of a pure holder with Toure storming forward but not always working back.
The best example of a box-to-box midfielder at the moment may be Juventus' Arturo Vidal. He is simply brilliant at absolutely everything and has experience playing in defence, midfield and attack. His incredible stamina means he's a prolific tackler and a consistent goal threat, and he's allowed to play such a role because of Juventus' unusual system. Andrea Pirlo provides the creativity from deep, which means the roles of Vidal and Paul Pogba -- effectively another box-to-box player -- are tasked with providing the energy in midfield. Because Pirlo isn't a great player defensively, however, Vidal and Pogba are forced to charge back into position too.
Something similar happened at Liverpool this season, with Steven Gerrard in the Pirlo role and Jordan Henderson -- or, to a lesser extent, Philippe Coutinho -- shuttling back and forth energetically. Henderson provided some decent flicks and passes on the edge of the opposition area, but his key feature remains his stamina. You could make a similar case for Aaron Ramsey at Arsenal in the sense that he was a Vidal-esque tackler and goal scorer simultaneously. A little like Toure at City, however, he could leave his midfield partner exposed and his side lacking in compactness. This remains the biggest argument against using box-to-box players: their failure at defensive transitions.
The modern interpretation of the box-to-box role is found primarily in Germany, a footballing nation most comfortable with the 4-2-3-1 system but where games are quicker and more direct than in Spain, with more turnovers. Various German players are capable of playing in box-to-box roles, albeit from a position as one of the two deeper midfielders.
Sami Khedira is a fine example, Toni Kroos and Bastian Schweinsteiger are more patient in possession but have the physical qualities while the Bender twins, Lars and Sven, are different types of players but still highly energetic all-rounders.
The Champions League semifinals of 2012-13 were also a good example, with Ilkay Gundogan storming forward repeatedly for Borussia Dortmund and Javi Martinez -- a Spaniard, but stylistically the most German of Spain's brilliant passing midfielders -- doing something similar for Bayern. The keys were that they picked their moments to attack and there was an element of control to their play.
Ultimately, that is what managers desire -- control. A few years ago, one of the most common ways to describe a great midfield performance was saying the player "covered every blade of grass." That's given way to discussion of pass completion rates, which neatly summarises the changing demands of central midfielders.
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ESPN FC's Craig Burley analyses the 17th and 16th ranked players in the #WorldCupRank.