We knew something had to give at Manchester United, what with the team's huge mounds of money begging to fill the huge holes in the squad, but it's still a bit of a surprise that the deal in hand is for Chelsea's Juan Mata, bought for a reported £37M. A bona fide world-class number 10 is a nice addition for a struggling side, but manager David Moyes has some thinking to do on how to incorporate Mata.
Man U this season, as in years past, play a sort of hybrid 4-4-2/4-2-3-1, mostly because of the style of Wayne Rooney. Rooney himself is sort of a hybrid 10/9, an exceptional finisher for a number 10 and extremely creative for a number 9. Depending on the situation, Rooney can be found dropping deeper into midfield, pushing back the other two central midfielders, or higher up the pitch as a more traditional striker.
To complement the midfield, Alex Ferguson traditionally liked to flank the center of the pitch with two pure wingers. The likes of Nani, Ashley Young, and Valencia are known for busting their ass up and down the pitch while hugging the touchline, only coming inside to blaze one over the crossbar.
Moyes has deviated from this a bit, at least on the left wing (he still favors Valencia on the right). Out there, he's fielded a Young/Shinji Kagawa/Adnan Januzaj rotation, with only Young being an out-and-out winger. Kagawa is a natural number 10, and Januzaj is a more creative wide player who likes to find space on the wing, then probe inside to pick the incisive pass. Kagawa's exploits on the left have been at best up and down, though Januzaj has been a revelation this year, often looking like the most dangerous man on the pitch when Rooney and Robin van Persie aren't playing.
So where does Mata fit in this scheme? That depends on his teammates. At the moment, with United's two best forwards injured, Mata could seamlessly slot in just behind Danny Welbeck. A full-strength United, however, would probably see van Persie up top, Rooney in behind, and Mata on the right—basically, a wide position that sounds a lot like the one he couldn't make his own this season at Chelsea.
Despite Mourinho's lack of faith in a wide-playing Mata, Juanny Cash does have experience starting on the wing. At Valencia, before his move to London, Mata was primarily a wide right player in a 4-3-3. This position usually doesn't require much defensive presence and, when in possession, grants the creative winger plenty of room to roam into central areas. It's essentially Philippe Coutinho's role at Liverpool when played alongside Suárez and Raheem Sterling.
So while Mata has excelled before playing out wide, the system he'll be joining in Manchester does present some potential difficulties, similar to the ones that consigned him to the bench at Chelsea—chiefly the defensive responsibilities. As the central guy in an attacking midfield trio, the number 10 really only has to press the ball when it comes around him. Once it gets past his position, he's free to loiter around with the striker, conserving his energy for the next attack. Wingers are asked to track back deeper, giving some resistance to the opposing fullback and at times even marking the other team's winger. In Mourinho's defensively solid style, he demands that his wide players defend. However, depending on the work rates of the other two attacking midfielders, a 4-2-3-1 can function fine with one less defensively-sound midfielder. Mata's not a complete defensive liability, so it's not unrealistic to believe Mata could fare well playing there.
Still though, that plan can work with one defensive liability. Januzaj, with his young legs, is willing to track back into his own half, but by no means is his defense more than just adequate. And while Rooney gets credit for sometimes dropping so deep as to make a tackle in his own penalty box, that sort of effort is—rightfully—the exception, not the rule. Wazza only has so much energy to expend out there, so it's best that it's focused in the attacking half. Substituting the one defensively sound winger, Valencia, for another guy for whom the best you can say is "well, he tries" is not the best way to cure the defensive issues that have been United's greatest problem.
The other tactical dilemma adding another number 10 is spacing. By fielding Januzaj, Rooney, and Mata behind a striker, you have three players most comfortable playing centrally. Number 10s usually thrive with the ball at their feet and everyone else moving around, presenting them with a number of options to cut through the defense. When everyone on the field prefers to drift centrally to find the ball, though, there isn't a ton of off-ball movement for whichever guy is currently in possession to capitalize on. The pitch becomes compact and there's no one trying to open it up.
Of course, there is every possibility that this transfer works like gangbusters. Let's not forget that Juan Mata was the two-time defending player of the year for a Chelsea team that won the Champions League (yeah, but still) and was fighting with compatriot David Silva for the distinction of best playmaker in the EPL. We have seen evidence that a team can pull off playing a bunch of central-minded mids. Arsenal has at times thrived while playing three ball-dominant central attackers—Mesut Özil, Santi Cazorla, and Tomas Rosicky—who realize the spacing problems and thus commit to constant motion. And Mata himself was great in a constantly-interchanging midfield alongside Eden Hazard and Oscar, neither of whom are traditional wingers. Plus, the team will now feature the more intricate, creative passing Januzaj has demonstrated was so lacking instead of the sprint to the byline, whip in a cross, wash, rinse, repeat style of Valencia. There is hope yet.
Ultimately, the success or failure of the Mata experiment will come down to the tactical nous of David Moyes. Mata's addition by no means solves all of their problems—in fact, a defensively sound central midfielder who can control the game remains the biggest need—but, if integrated properly, he will definitely improve what has been an unimaginative offense. Will Moyes find a way to adapt another number 10 in the side, despite his failure to accommodate Kagawa? Like it or not, in Moyes United fans must trust.