Globo.com reports that a negotiation is ongoing to extend Martinelli's contract with Fluminense until the end of 2030. The extension is a recognition of his importance to the team and is intended to provide security to the club, especially as interest from European clubs grows.

Clubs from the Gulf submitted offers for 24-year-old Brazilian defensive midfielder Mateus Martinelli, according to Brazilian website ge.globo.com. The offers were rejected by Fluminense. The proposals from these clubs and others were for 12 million euros. Fluminense values Mateus Martinelli at a minimum of 20 million euros. Mateus Martinelli is under contract with Fluminense until 2027. The club intends to sign a new contract with him until 2030. West Ham, Beşiktaş, and Olympiakos have also reportedly had offers of a similar value rejected. In the current 2025/2026 season, Martinelli has made 3 appearances and provided 1 assist in the Campeonato Carioca, along with 1 appearance in Série A. His current market value is estimated by Transfermarkt to be €14.00m.