The 19-year-old appeared as a substitute in both of England's recent friendlies against Chile and Germany, having made his debut at senior international level in October against Moldova.
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"I don't think it is the time to consider that (the World Cup) - the squad is going to be announced in June," he told reporters.
"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.
"In football you need to concentrate on the day-to-day work and that's where Ross is. He is enjoying his experience with England, and when he came on yesterday he was himself and that is always important.
"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. Then the reward is always around the corner, after your good work on a daily basis.
"Sometimes you get confused as a player how you are going to affect what happens in the national team, but it is very easy. It is what you do at club level."
Everton players Phil Jagielka and Leighton Baines were also in Roy Hodgson's latest England squad, and Martinez insists that the fierce competition for places will only make the national team better.
"It is normal. You are going to get this sort of debate," he added. "You are looking at probably one of the best World Cup events ever.
"There are many possibilities for the national team manager to consider and I am sure that is going to happen over the next five to six months.
"It is a great position for the England squad to have the quality of the players they have, particularly in that left-back spot.
"You have seen in the last two games, three really good footballers but from our point of view Leighton is a special footballer in the best moment of his career.
"He had a really important role in the two (October) qualifiers but it is now about getting back to club level and making sure he has a very strong season."