If Mata moves to Old Trafford will he rescue their season or falter under a failing manager at a collapsing club?
Any club breaking its transfer record for a player must expect him to make a difference. A club in the grip of a crisis, whether real or imaginary, will expect him to make an immediate difference. When Arsenal shelled out £42.5m for Mesut Özil in the summer they achieved their objective straight away. The German made an instant impact, both on the pitch and in terms of dispelling the negativity that was beginning to suffocate Arsène Wenger's side, and Arsenal have been reaping the benefit ever since.
The question now is whether Juan Mata will turn out to be United's Özil. The comparison is perfectly valid because both players are the same age, fill broadly the same position and will cost similar amounts. But it overlooks the fact that United could have had the real Özil, not just an out-of-favour imitation, had David Moyes shown any interest when Real Madrid offered the player in advance of his move to Arsenal.
The Manchester United manager is not known for his decisiveness in the transfer market. Neither, it could be argued, is Wenger, though despite Özil being hawked around leading clubs as Real Madrid sought to raise money and free space for the capture of Gareth Bale, Arsenal still managed to present their new signing with something of a conjuror's flourish. The fans were begging for a big signing, something to show intent, and Wenger silenced them with a pleasant surprise. As a result of the stealth of the operation Özil was able to join his new club under relatively little pressure and begin looking like he was doing Arsenal a favour rather than the other way round.
Most of that, one feels, will be missing when Mata runs out in a United shirt. The club have bought him because he is available, not because he is a player Moyes has always rated or coveted. Moyes's reasons for not wanting Özil in the summer included the consideration that he already had Wayne Rooney and Shinji Kagawa for the position just behind the main striker – and he still has, even if Rooney is becoming restless and Kagawa has generally been disappointing since arriving in England.
Mata is possibly more of a winger than Özil, or at least that is how he has mostly been used at Chelsea, but Moyes is not short of wide players and United's traditional reliance on width and crossing is beginning to be questioned anyway. Mata's talent lies in his cleverness, his ability to spring surprises and offer creative vision beyond the scope of most players, hence the comparisons with Özil.
United certainly need some of that, possibly all of it, though there must be a reason why José Mourinho has not been picking him. Mourinho has doubts about Mata's pace and strength, primarily, and it would be ironic to see a rival manager whose Everton teams were noted for their robustness and whose major signing so far at United has been Marouane Fellaini take him off Chelsea's hands.
Desperation is the word some might use. If Fellaini is now wondering where he stands in the pecking order, he joins a list that includes Kagawa, Ashley Young, Nani and Antonio Valencia. There would not be too much wrong with a front three of Adnan Januzaj, Rooney and Mata playing behind Robin van Persie, but as United have three of those four players at their disposal already, albeit with two of them inconveniently injured, there is a sense of sending for Mata as a one-man rescue mission, someone who will turn up like Eric Cantona, puff out his chest, pull up his collar and get to work on restoring United to their former glory.
Mata may or may not be able to do that, but together with the fee – Cantona was not only an inspired piece of left-field thinking on behalf of Sir Alex Ferguson, he came at a bargain price – it amounts to a great deal of pressure on a single player.
Özil still stands as an example of how a single transaction can transform a club, though there are important differences between Arsenal and the present United. One is that Wenger is a long-established and historically successful manager with a philosophy of how he wants the game played and a keen knowledge of the players who would be able to fit into his system. Moyes might have been in the same position in his later years at Everton but he is a long way from such comfort and stability now.
Another is that Arsenal, for all their long trophy drought, have remained a club of impeccable pedigree, always in the Champions League, rarely out of contention for domestic honours and usually capable of giving the leading lights in Europe a run for their money. United could count themselves in the same bracket until recently but, if it has reached the stage where they cannot get past Sunderland in a semi-final at home, or even take a decent penalty in a shootout, none of the old assumptions are valid any more and a club in turmoil – if not crisis – is never an attractive destination for a top player.
Mata, as it happens, was the only Chelsea player to miss a penalty in the 2012 Champions League final, but as he makes his way up the M6, amid dozens of variations of jokes about u-turns and emergency stops, that will be the least of his worries. His primary concern is that, for all the money involved and United's rich tradition and history, he is about to sign for an ordinary club with a manager who has a gift for making everything he touches turn to wood.
Even the most basic question any new signing must ask himself – how long will the manager who wants me stay in control? – cannot be unequivocally answered. Arsenal ushered in Özil as a breath of fresh air, an exciting new chapter in the club's history. United would love to do the same with Mata, yet the deal is already being presented as a quick fix, a kneejerk response, maybe even the last roll of the dice for Moyes in the transfer market.
The good news for Mata is that at least the United fans want him. A straw poll conducted by the Manchester Evening News found strong support for the idea of a swap with Chelsea with Rooney travelling in the opposite direction. The bad news is that it was held in the summer, when it was briefly suggested (then denied) that Mourinho might make Mata available as part of his pursuit of Rooney.
Going for Mata at that time would have made sense for United. It would have been a statement signing for Moyes that would have appeared to weaken a rival. Words such as "bold" and "audacious" would have been used, as they were with Özil. Mata's capture is not being described in such terms now. Not because he is any less of a player, but because within six months United have become so much less of an entity. It is already being suggested that far from emulating Özil, Mata's move to United could have more in common with Joe Cole's unhappy transfer to Liverpool.
That may seem harsh but these are strange times. No signing at the moment, no matter how stellar, will be greeted with complete confidence until Moyes and United can prove they are good for each other.