Mata's future has been the subject of speculation throughout the summer and he was linked with a move to Manchester United as part of Chelsea's bid to try to sign Wayne Rooney.
The Spain international's omission from the Chelsea team which drew 0-0 at Old Trafford on Monday night only served to intensify rumours he could be sold before the transfer window closes.
Chelsea's impending signing of Willian will increase competition for places, even though Jose Mourinho has insisted that Mata is not for sale.
There were reports that Juan Mata senior, the player's father and agent, was at the Emirates Stadium to watch Arsenal's UEFA Champions League tie against Fenerbahce on Tuesday night, but Wenger has suggested a deal would be a long shot.
"I like him," said Wenger, who was beaten to the former Valencia playmaker's signature by Chelsea two years' ago.
"I watched the game last night and I've heard, like you, Juan Mata could be on the market.
"There is anyway in England a reluctance to sell to each other."
Speaking after the draw against United, Mourinho had said: "He is very important for me and very important for Chelsea.
"The stories that are coming out are nonsense stories. He goes nowhere."
Fresh reports have also claimed that Tottenham Hotspur may try and swoop for Mata if Gareth Bale moves on, while Atletico Madrid have also been credited with an interest in the 25-year-old.
Atletico president Enrique Cerezo has admitted he is an admirer of Mata, but has played down talk of a transfer by admitting he would probably cost too much.
Cerezo was quoted as saying in The Sun: "Mata is a good player but he's playing in the Premier League and over there they pay a lot."