In response to Wenger's comments, Mourinho said in a press conference: "Arsene Wenger complaining is normal, he always does, but when a player plays for a club on August 20 and then on September 5 plays for a different club this is normal. This is the market.
"If Arsene Wenger sold Mesut Ozil to Manchester United I would be happy because they are losing a very important player, like we are with Juan, but this is his nature.
"What is not fair is that his team always gets the best days to play. Always. This weekend you want to play early to recover. Who plays Friday? Who plays Sunday?"
Mata is yet to complete his move to Old Trafford, but reports have claimed that the deal is worth around £37m.