The Daily Mail says the midfielder dubbed 'the new jewel of Brazilian football' has been hit with a £21million buy-out clause after reports linking him to Manchester United.
After recently turning 18, the skilful Under 19 international signed a new deal at the Brazilian league leaders, increasing his buy-out clause from £5m.
He has been highly praised by coaches and team-mates but the teenager said, modestly: "I don't have think about this. I only have that to play football.
"I face this with calmness. I am not a star."
Many observers have compared him to another Gremio talent who is already playing at Old Trafford - Anderson - and believe Douglas Costa is showing more promise at this early stage of his career.
If United are not put off by the price-tag he would join Anderson, Rodrigo Possebon and the Da Silva twins - Rafael and Fabio - as part of a growing, youthful Brazilian influence at Old Trafford.