The Champions League is the only competition United have a chance of winning in this campaign.
But United boss Moyes said: "We wanted to get Mata when we could and that was the January transfer window.
"Yes, it's a frustration we can't use him in the Champions League and that's why you hear people saying January isn't a great time to buy.
"Most of the clubs are trying to buy players who aren't Champions League cup-tied.
"But the better ones tend to be - like Juan. We are
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