The curious case of Shinji Kagawa has been something of a mystery since his £17m signing from Borussia Dortmund in June 2012.
His signing seemed to make sense for United at the time - a talented young creative midfielder, capable of moments of magic and proven at the top level of European competition. But under Sir Alex Ferguson, and later David Moyes, Kagawa has failed to make an impact on the United first team.
On Tuesday night against Bayer Leverkusen he looked lost on the left wing, struggling to get a foothold in David Moyes' hard-working United side.
Perhaps similar to mercurial playmaker Andrei Arshavin's experience at Arsenal, Kagawa may need to leave Manchester United to regain his best form.
Whether for tactical, fitness or other more enigmatic reasons, Kagawa has been consistently played out of position or not at all for Manchester United since his arrival.
A large proportion of United fans feel Kagawa hasn't had a fair crack of the whip, and that his undoubted potential means he should be given a run of games in his favoured position to pull the strings at the head of United's midfield.
It's hard to argue the difference between Kagawa at United and at Dortmund is insignificant.
His goal return in the Bundesliga was a massive part of Dortmund's double-winning 2011/12 season, with 17 goals and 14 assists for BVB showing how well he performed in Dortmund's high-pressing counter attacking style.
Perhaps Kagawa's specialist talents have put off his Manchester United bosses from giving Kagawa a chance in his favoured central role. Certainly, his main rival for the position in Wayne Rooney offers a certain strength and determination that Kagawa sometimes lacks, and the form of the England forward would make him difficult to drop.
But David Moyes' perplexing treatment of a player such as Kagawa shows signs of a rigid management style. He is loath to adapt his style to the team's best players, and would rather build a midfield on strength and solidity than guile and flair.
The summer acquisition of Marouane Fellaini certainly illustrates the kind of midfield that Moyes would like to build at United.
There have been notions that Kagawa's international duties as a key player for Japan has left him jaded in the early part of this season, with long trips around the world for World Cup qualifiers scuppering hopes of a good start to the Premier League campaign.
But even rested and match fit, Moyes' insistence of playing Kagawa out of position to include Fellaini in the squad points to a manager that doesn't quite understand how best to include a player of Kagawa's quality in the team.
The Japanese internaitonal has been publicly critical of his lack of game time, and will reportedly consider his options if his prospects do not improve. Dortmund coach Jurgen Klopp would welcome the Japanese international back to the Bundesliga.
Kagawa needs to take a look at his future over the next few weeks. If he finds himself marginalised behind the likes of Anderson and Giggs, he will understand his place in Moyes' reckoning. Cutting his losses at a wasted time in Manchester could be Kagawa's best move.
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