After the teenage forward, at Goodison Park for the season, impressed again with a late equaliser against Arsenal, the Toffees boss revealed that the club have an option to extend his deal for another year if the Blaugrana agree.
However, Martinez insists that no decision on the "special" youngster's future has been made, while praising him for his quick adaptation to the Premier League.
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"He is such a special footballer, one that anyone would enjoy watching. He's adjusted to life in the British game and understands what is needed - and he has done that quicker than we expected.
"We have an agreement [with Barcelona] over 10 months - it would be ridiculous to sit down now about the next step. We're all happy and will leave it until the end of the season and see where we are.
"If he does really well, the chances of having him longer are slim."
Martinez was also enthusiastic in his praise another of his young stars, Ross Barkley, following the England international's much-trumpeted performance against the Gunners.
"He takes everything in his stride," the manager added of Barkley. "He's got all the attributes to be a great player.
"He never gets fazed by the situation; I don't think the scale of the game affects Ross. He's one of those players who is capable [of performing at the top level] but it is important to measure him on a weekly basis to make sure he doesn't burn himself out."