It hasn't been a good season for Iker Muniain, Athletic Bilbao's 'jewel in their crown'.
At just 19, he helped tear United apart, scoring at Old Trafford and leading the way in a 3-2 victory.
The plaudits quickly came his way, he was even dubbed the 'Spanish Messi' by the media in southern Europe, with a £20 million price tag place on him to try and deter buyers.
He ended the 2011/12 season with 10 goals and 10 assists, helping Bilbao reach the finals of both the Europa League and the Copa del Rey.
This season, he hasn't been nearly as successful. In 27 games for his club he has just one goal and three assists.
That one goal came in a Europa League qualifier against Croatian minnows Slaven Balupo back in August; he hasn't found the net since.
His troubles can be traced back even earlier, ahead of Spain's ill-fated Olympic football quest for Gold, he was tipped as the player of the tournament.
He failed to make an impact, and Spain flopped, being knocked out in the group stages, trudging back to their homeland with their tails between their legs, unable to match the senior side's Euro 2012 win.
Muniain's last assist came back in early October, with just one in La Liga, and the attacker is clearly struggling to live up to expectations. But why?
That is the £20 million question, and the versatile attacker has been trying his best to find an explanation for it this week.
Is it because of a breakdown in trust between himself and coach Marcelo Bielsa? Is it because the rest of the Bilbao team are struggling or being linked with at exit, following key man Javi Martinez who left in the summer?
Here's what he had to say:
"My drop in form is due to a bit of everything, but the main thing is that I was not fully fit, (fitness) is critical to my game and at times it has influenced things. However, the Betis game showed that I am recovering and am much better than in previous games.
"Was I angry at being replaced in that game? I was doing well, but obviously I have to respect the coach’s decision,
"I was angry with myself because every player likes to play every minute. When I don’t get angry for leaving the field, that is when you should worry."
Speaking about the last few months and teammate Fernando Llorente's impending exit, he said:
"Maybe the last few months have not been good at heart for all that has happened, I like him a lot and I wish him well. I always like to have him around here but it's something for him and the club to solve." (Llorente has since clinched a summer move to Juventus.)
Bilbao currently sit in just 14th, and on current form face an uphill task to finish in the top half of the La Liga table.
If they are to do so, it will be dependent on Muniain regaining top form. It is no surprise to hear the player discussing his fitness as a main contributory factor in his slump.
Last season he featured for his club a staggering 59 times, plus eight times for his country at senior, Olympic, and under-21 level.
67 appearances in one season is too much for any player, let alone a player just 19 at the time. Muniain's drop-off should re-ignite the debate about player 'burnout' - and underline why managers are right to try and 'protect' their youngsters from playing too much football at a young age.
Can Muniain bounce back? Is a big money move what he needs or is it too soon?
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