The former FC Porto player is frustrated at slipping down the pecking order at White Hart Lane, according to a report in the News of the World.
Mendes, who missed the final two months of last season with a broken toe after a good initial start to his Tottenham career said: "If I am out of the picture then I will leave. I will return to Portugal, I don't want to be ignored anymore."
"There has been talk of a return to Porto but nothing has materialised. We have to wait and see." Three into two doesn’t fit and following the arrival of Jermaine Jenas any opportunity in the future for Mendes looks increasingly less likely.
However, Jol called on his array of central midfielders to perform better in the final third or risk a repeat of narrowly missing out on European qualification like last time around.
"It’s a big challenge for me and the players this season. What we must do is improve our productivity. It is about getting the qualities we have to come to the surface," he said in The Times newspaper at the weekend.
"Jenas scored one goal last year. He should score six or seven. Brown scored one goal. He should score five. Michael Carrick is not scoring a lot of goals although he has had more shots on target in the last couple of games.
"Teemu Tainu scored three goals and Edgar Davids can score four or five goals," he said of the newboys to the Premiership.