I like Mata. His first touch is out of this world, his close-range freekicks are a constant threat, and in terms of passing the ball around, he's a true Spanish midget. He's also incredibly likeable.
But as I've always said(and predicted); Mata is his goals and assists. The moment he stops scoring and assisting constantly, he's unfortunately a very limited player. And those times are sure to come, because unlike Rooney, who is a striker at heart, he doesn't have the same energy and individualism in his game. He's dependent on the ball rolling his way. When it doesn't, he's essentially only good for keeping possession and freekicks.
Having said that, I'm surprised that Mata has become this limited already. It's actually reached the stage where I'm starting to want to see Rooney in the no.10 position instead. And that's saying something, as I've always been opposed to this idea.
The three no.10's we've had since january have had different strengths and weaknesses:
Rooney
+ The strongest individualist(nature of a striker)
+ Can guarantee goals and assists
+ Hard-working
- Offers effectively no linkup between midfield and attack
- Not good at keeping possession under pressure
Mata
+ Generally scores and assists a lot
+ Excellent at keeping the ball in the team(good passing and makes few mistakes)
+ Set-piece specialist
- Very dependent on the ball rolling his way
- Generally limited skillset once you isolate his goals and assists(no speed, can't dribble, bad defensively, low energy)
Kagawa
+ Versatile(hard-working, decent speed, good technique, good at passing, good at intercepting, decent finishing)
+ (Was) our best player at linking up(especially on the counter)
+ If we take goals/assist out of the equation, he generally offers more than Rooney and Mata
- Lacks individualism. Will not save our ass on a rainy day.
- Can't guarantee goals and assist to the same degree as Rooney and Mata(doesn't have "Striker's Instinct").
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The truth of the matter is that none have been ideal for us. Rooney is not ideal in the no.10 position regardless of style, but he gets a free pass because of his energy and goals/assists. Mata is ideal for the no.10 position when we dominate games with technical football, but we're not good enough to do that yet. Kagawa was our most balanced no.10, but he couldn't save our ass on rainy days(which there were plenty of under Moyes). Combine this with the fact that he couldn't guarantee goals and assists the way Rooney and Mata could, and it became a gamble to play him.
Long-term, I still think Kagawa would have been the best choice, but that's a different story. I haven't given up on Mata yet, as he will come good when the team comes good. The question is: how long does it take before the team comes good? And will Van Gaal be patient enough to wait that long?