Juan Mata a chink of light in Manchester United's gloom

Share price tremors, night-time visions of the Europa League and apocalyptic media commentaries: all contributed to Manchester United's 37 million pounds signing of Juan Mata on a day when a semi-final second leg of the Capital One Cup assumed the importance of one of the great winter football nights at Old Trafford. The prize: a date with Manchester City at Wembley.

The punishment for going out: a ravaged season, with the Premier League title defence blown by January, the two Cups heading elsewhere and a Champions League campaign intact but promising very little. City, meanwhile, are fielding inquiries about a possible quadruple, following an aggregate 9-0 win against West Ham United in the other semi. Municipal life was starting to feel profoundly uncomfortable for the city's traditionally dominant club.

Panic buy, PR move, great transfer-market grab, season-saver: the Mata raid is all things to all men, but nobody could dispute that it would improve a mediocre (by their standards) United midfield, which for this fixture featured the slightly stranded grace of Michael Carrick and the courage-in-the-face-of-adversity of Darren Fletcher, with Adnan Januzaj probing the right and Shinji Kagawa to the left behind two strikers: Danny Welbeck and Javier Hernandez. The Mata deal shed light all at once on United's weaknesses and strengths.

First, Jose Mourinho would rather take a 12-month vow of silence than sell a match-winning midfielder to a title race rival. Chelsea's step up to the bargaining plate came after Mourinho had extinguished United's title defence with a 3-1 victory at Stamford Bridge on Sunday. From that moment on he could pat David Moyes's men on the head and wish them well in the scramble for fourth. But United, like Arsenal in the summer with Mesut Ozil, are still sufficiently strong to be able to solve a problem by throwing money at it, both in the PR sense of dousing fan anxiety and improving the side in troubled times. When Moyes took over the word was that United were not fussed about buying a big-name No?10. The new manager had Shinji Kagawa and Wayne Rooney and felt Januzaj might develop into a central playmaker. Though big names were pursued (or inquired about) - Cesc Fabregas, Gareth Bale, Cristiano Ronaldo, Leighton Baines and Ander Herrera - Moyes contented himself with Marouane Fellaini, whose injury has at least sheltered him from the scepticism of the Old Trafford crowd, which has measured out its life watching Paul Scholes and Roy Keane.

By the autumn, though, it was already obvious that Moyes's first-team squad had fallen behind those of City, Chelsea and Arsenal. To a nurse or teacher, the idea that salvation can be found only by breaking the club's transfer record for a player who is surplus to requirements at Chelsea would seem a grotesque affirmation of football's one-track mind. In the economics of modern football, though, the Mata move makes sense, even if it comes without tactical forethought. Moyes thought there was enough midfield creativity at his disposal.

Results said he was wrong. So Mata has become United's Ozil: an expensive, safe buy in times of need. The anomaly of Dimitar Berbatov being United's record signing at pounds 30.7?million is about to be wiped from history. Artistry is certainly in short supply in this side. They are more direct, less fluid and display much less conviction in possession of the ball. Each time we say this the absence of Wayne Rooney and Robin van Persie demands a mention.

Even Sir Alex Ferguson's teams would have been emasculated by the loss of one of Europe's best strike partnerships. In a sunlit world where Rooney and Van Persie are both fit then the question is how to deploy Mata in a way that allows his safe-opening expertise to shine. In the centre, is the best and easiest answer. There is no point in Moyes building the team round Rooney when the odds and the grapevine point to a move away by England's senior striker. So United cannot worry about Mata dancing on Rooney's toes. Nor could Kagawa grumble about losing the orchestrator's role. Lacking authority and bite in the No10 position, Kagawa has been forced wide, where he lacks the inclinations of a winger, and so ends up floating without posing any consistent threat. The rest of the central midfield cast - Tom Cleverley and the ageing Ryan Giggs - could not stand between Mata and his calling as the team's main improviser.

By degrees, playing two strikers is becoming less of a heresy for which managers are burned at the stake. A United side with Rooney, Van Persie and Mata ought to generate more excitement than anxiety about how the three could play together. This cup tie accentuated the lack of rhythm in United's passing. Though they took the lead through a Jonny Evans header on 36 minutes there was never the sense that Sunderland had stumbled into the kind of Old Trafford ambush the crowd here have witnessed for decades. It may seem patronising to Sunderland to remark that this was a proper contest. Yet there was a time when United would have torn relegation-threatened opponents to shreds. After underbidding last summer - or not chasing targets with sufficient vigour - United are going to have to overpay this winter. Selling clubs will know a hint of desperation has crept into the rebuilding. They also know about the Glazer debt burden.

A 150 million pounds transfer budget might feel more like 100 million pounds after United's weakened bargaining position has been taken into account. As things stand Champions League football next season is not a perk they can promise transfer targets. If the Mata story lifted United's spirits, their defects remained all too visible here.

The need for fresh talent was obvious. If the Mata buy looks a bit forced, at least he is the right type of operator. A player with skill and soul.