According to Globo.com, Martinelli stated he has received different proposals to leave Fluminense, none of which satisfied all parties involved. The player admitted he desires to play in other countries but said he will only leave the club if a future offer is good for all parties. Martinelli confirmed there have been proposals that were good for him but not for the club. He also declared that every player dreams of playing in the big leagues and that he has that dream as well.

Offers of approximately 12,000,000 euros were submitted by clubs from the Gulf for Mateus Martinelli, a 24-year-old Brazilian defensive midfielder, but Fluminense rejected them. Fluminense values the player at a minimum of 20,000,000 euros. Martinelli is contracted until 2027, and Fluminense wants to extend his contract to 2030. The player has a current Transfermarkt market value of €14.00m. In the 2025/2026 season, he has made 3 appearances and 1 assist in the Campeonato Carioca, and 1 appearance in Série A. West Ham United, Beşiktaş, and Olympiakos Piraeus have also been linked with him.