The 23-year-old helped the Seleção lift the trophy on home soil this summer, scoring in the final as they beat Peru 3-1.
Arsenal have been heavily linked with a move for the player, although other interested clubs include Milan and Atletico Madrid.
Everton admitted that he already has a proposal on the table, although the identity of the suitor remains unknown.
"At this moment I have an offer, but I can't say the name of the club," he said, as reported by the Mirror.
"Just like I can't promise that on Thursday I'll still be playing for Gremio, we'll see."
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