I'm absolutely fine with this. As a squad option, and with us potentially having a huge number of fixtures next season what with being in the EL, we could do a lot worse than Mata as a back up option. I'm always amazed by the level of vitriol Juan seems to be on the receiving end of from certain sections of our fanbase. Whilst he's obviously past his best, the idea that he contributes nothing and is "finished" is nonsense to me. He still makes a difference when utilised correctly, we saw this in several games last season, and we often get better results with him in the squad than out of it (after the PSG win, the only four games we didn't lose after that point were the four games Mata started).
I often find if Mata has a good game, his contribution is downplayed or even outright ignored or forgotten - as mentioned earlier, he had several good performances last season, but according to a lot on here, he did nothing. Yet when the whole team plays bad, Mata is often unfairly made the scapegoat, whearas certain other worse performing players are excused. People are always quick to mention how he never lived up to his price tag, but then ignore how he's been constantly misused and played out of position by every manager he's played for, yet still manages respectable stats. He never complains, has an exemplary attitude, always looks as if he's trying, yet he's constantly dumped on.
I know people always mention how "loved" Mata is by Utd fans - I actually think he's one of the most underrated, underappreciated players the club has seen in a very long time.