Mata hasn't played wide for Valencia all year (at least, not 'wide' as in winger wide, like the year previous), he's spent a lot of time centrally, even playing as a pseudo CF in some games. Other games as part of a midfield 3, and he's looked far from out of place.
He can cross with both feet, score with both feet, tackle, pass. Comfortable with playing wide on both sides, off a striker, in midfield ..
How does that not fit the bill? he's perfect to play the role Raul played for us last year, and his ability to play pretty much any attacking or playmaking role makes him a substantial upgrade, imo.
If anything he's looked better not playing wide for Valencia this year.
http://www.youtube.com/watch?v=pysvlxoBA1c
(ignore the crappy music, you have been warned!)
Mata's a winger/forward, he's not a midfielder. The Meireles/Houghton role is one of a midfielder that has license to roam forward but also a greater responsibility defensively than somebody who'll play in the Barnes role. And like I said, he'll also provide us with an option of switching to a 4-3-3. Mata won't play CM, not even as part of a 3 man midfield.
If we signed Mata and we play the system above, he'd play the Barnes role. Barnes didn't just hug the touchline, he also had the freedom to come inside and like Mata, he scored a lot of his goals playing infield too.