As we all know by now, the unsettled Juan Mata has definitely probably more or less moved to Manchester United. He still has to turn his head and cough for Manchester United's medical staff, but that's probably a formality, and United will hope to have him in Manchester for Tuesday's game against Cardiff City.
On the one hand, I'm not sure I care, as an Arsenal fan - players move from club to club all the time, and this doesn't involve Arsenal in any way, so my first instinct is to ignore it all and go about my day. But then I look at the fixture list, and I see that Chelsea have already played Manchester United twice, and Arsenal have only played them once. Is that a sort of gamesmanship move by Chelsea? If so, it's kind of a curious one, given that Chelsea are also Arsenal's title rivals, and that Arsenal still have to play Chelsea once more in March; Mata hasn't seen much playing time this season, sure, but it's an odd move nonetheless if the thought is that a Mata sale would decrease Arsenal's title chances.
There might also be FFP ramifications to it - I'm by no means an expert (or even all that conversant) in the minutiae of FFP, but it's fairly well known that Chelsea are one of the clubs that might struggle to adhere to FFP guidelines, so the Mata sale might have been an effort to balance the books? Maybe?
I'm also not sure I care about the "CHELSEA SHOULDN'T SELL TO A DIRECT OPPONENT" thing people have been talking about - Mata is a saleable asset who was surplus to requirements, and United are a willing buyer, and that's how capitalism works. After all, Arsenal sold a certain Dutch player to Manchester United and made a nice tidy profit off that bit of business, so it's not like Wenger can have a problem with the Mata sale.....ooops I guess he does.
So, long rambling story short - Mata's a United player now, and as long as Arsenal keep winning games, it doesn't really matter from an Arsenal perspective, at least to me.