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The 20-year-old midfielder, who enjoyed loan spells with Sheffield Wednesday and Leeds United in the Championship last season, has displayed superb form after gaining a regular first-team place under Martinez.
Barkley's performances have helped Everton to fifth in the Premier League table, and he has also broken into Roy Hodgson's England squad.
Article continues below"In football a week is an eternity, so for a few months it is going to be a waste of time thinking about what can happen in the future," said the Spaniard.
"You need to concentrate on the day-to-day work and that's where Ross is.
"But all he needs to do now is concentrate on his club role and make sure he is ready to help the team and enjoy his season and develop, and grow.
"Sometimes you get confused as a player (about) how you are going to affect what happens in the national team - but it is very easy. It is about what you do at club level."
