The Spanish midfielder is in the dark over his future at Old Trafford and has yet to be offered a new deal by club bosses.
With just eight months left to run on his contract, this has left the door open for the Gunners to swoop in.
Arsenal boss Unai Emery is thought to be keen on reuniting with his former Valencia colleague.
The Mail report that Mata – who is on £140k per week – is waiting on an offer from United, but would be free to discuss terms with prospective new clubs in January.
The 30-year-old would prefer to extend his deal with the Red Devils, but would move in order to stay in the Premier League and has also attracted interest from La Liga.
Mata is one of the United players who has endured a difficult relationship with United boss Jose Mourinho in recent months.
However, important strikes in recent games against Newcastle and Juventus could see Mata back in favour in the starting line-up.
Both goals were sublime free-kicks that helped United come back from behind to win both games.
Mata revealed that he pleaded with United captain Ashley Young to take the free-kick that got his team back on level terms against Juventus in the Champions League on Wednesday night.
“As soon as there was the free-kick in there, I had the confidence that I had to take it,” he said.
“I told Ash ‘please let me take it, because I can go over the wall’. It’s very difficult for the goalkeeper because they don’t see a lot.
“I think because of the venue and the importance of the game, it’s one of the best (I’ve scored).”
Mata has scored 42 goals in 198 games for the Red Devils since joining from Chelsea in 2014.
He has since won the FA Cup and League Cup, as well as the Europa League with the club.
Mata also has 41 caps for Spain, scoring ten goals.
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