The Spaniard's imminent arrival in a club record deal will be a massive boost for United and proves the club can still sign top players - but it's just the start of rebuilding.
United sunk to a new low in a dismal season on Wednesday night as the club was dumped out of the Capital One Cup following a semifinal defeat on penalties to Sunderland.
Untied was outplayed by the team 19th in the Premier League, clueless on the ball and lacking any ideas. The gameplan appeared to be to play for a sneaky victory on away goals over 120 minutes - one which fell to pieces during an abysmal shootout in which only Darren Fletcher managed to score past Vito Mannone.
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United is 14 points behind the Premier League leader, out of the two domestic cups and the only target for the remainder of the season must be to scrape a top-four finish. It is some fall for the same side that won the league by 11 points last season under Sir Alex Ferguson.
Of course there is an element of panic in the move for Mata, which should be completed after the Spanish playmaker undergoes a medical on Thursday. United has plenty of No.10s in the squad - not least Wayne Rooney - but in this situation the club simply cannot pass up the opportunity to sign a world-class player.
Nor can the club wait until the summer. Having embarrassingly failed to land a string of summer targets including Cesc Fabregas and Gareth Bale, United needed a statement signing to aid the ailing atmosphere around the team.
While Mata’s arrival will boost a team playing with zero confidence, do not expect the transfer to have the same impact as Mesut Ozil’s move from Real Madrid to Arsenal last summer.
The signing of Mata is just stage one in a massive rebuild at Old Trafford. Moyes has 180 million euros to spend and also wants to sign a central midfielder, left back and central defender. He will try to sign at least two more players before the January transfer window closes next week.
Whether he plays in a central role or from a wide position, Mata will vastly improve United’s attacking options. He certainly needs a central midfield leader behind him, but his record of 19 goals and 34 assists from 61 games in the 2012-13 campaign point to a player who makes a difference around the edge of the penalty area.
Injuries to Rooney and Robin van Persie have hampered Moyes, with United losing four out of its first five matches of 2014, but their absence has also laid bare the startling lack of quality in the squad.
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More than anything, United needed to make a statement. It proves that the team can still attract top players to Old Trafford. United has the money and ambition to create a squad that can once again challenge for titles. It gives Moyes something to work with and towards.
It says a lot about United’s fall that Jose Mourinho was willing to sell Mata to the Manchester club, presumably no longer seeing Moyes’ team as a rival, even in the medium term.
While other areas of the team may be more in need of immediate attention, there will also be implications for other members of the squad.
Mata prefers to play as a second striker, the role also preferred by Rooney. In many ways, the 25-year-old can be seen as a ready-made replacement for Rooney, who is still a target for Chelsea and increasingly expected to leave in the summer, when he will have just one year remaining on his contract.
Shinji Kagawa, meanwhile, can reasonably conclude that his time at the club is up and will seek a summer transfer, possibly back to Borussia Dortmund.
It will also take the pressure off Adnan Januzaj, the single ray of hope in a dark season for United. The teenager also prefers a central position but can continue learn his trade playing off the right side.
Mata will double his £70,000-a-week wages to sign for United but the Spaniard is driven by a desire to play regularly having started just 11 of Chelsea’s 22 league matches this season.
He will feel he has a point to prove, not only to Mourinho but to Spain manager Vicente Del Bosque ahead of the World Cup this summer.
In a miserable season for United fans - something they have not experienced for decades - signing Mata is a phenomenal start in getting back on the right track.
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