Matas current contract expires at the end of the season and United are yet to make the Spaniard an offer to remain at the club.
The Daily Mail claim Mata is completely in the dark over his future at United and is still waiting for the club to make their move.
With confusion about Matas position at United, Unai Emery is waiting in the wings to take advantage.
The Arsenal boss worked with Mata in their Valencia days and would love to have the 30-year-old at the Emirates.
Mata is currently earning £140,000 a week at United and would want to stay in the Premier League should United look to offload him.
United triggered a 12-month extension in Matas deal at the end of last year, and the forward reminded Jose Mourinho of his worth in the stunning comeback win over Juventus in the Champions League.
Mata sparked Uniteds fightback against the Italians, curling in a free-kick before the Red Devils grabbed a winner at the death.
However, Mourinho and Mata have not always seen eye to eye and have an up and down relationship.
Mourinho was the one who sold Mata to United when he was still Chelsea boss, and the attacker has struggled to win a regular place in the Red Devils starting eleven.
Mata has offers from Spain and could return home after seven years in the Premier League.