Renato Gaucho has conceded Gremio will struggle to keep hold of prize asset Luan now the transfer window has opened in Europe.
The 24-year-old was part of Brazil's gold-medal winning side at Rio 2016 and has made a significant impact at club level with Gremio ever since.
And it is no surprise given Luan's recent form of seven goals in eight games in all competitions, helping Gremio to second in the fledgling league table and the last eight of the Copa Libertadores.
As a result Renato expects the European clubs to begin circling and Gremio are unlikely to be able to keep him in Brazil.
"In my opinion, Luan is the best player in Brazilian football," he told SporTV. "He has been playing great football, helping the team.
"We all know that Gremio will struggle to keep him because the proposals will appear.
"We hope he does not go, but it gets difficult with the [transfer] window and with him playing as he has been playing.
"It's going to be a real shame. The group are strong, but of course we will feel it if this happens.
"For my part the club would never interfere in a way that holds back the player. Unfortunately nowadays the Brazilian clubs cannot compete with [those in] Europe."
Luan made his Brazil debut in January's 1-0 friendly win over Colombia, the forward playing the final 27 minutes in Rio.