The Selecao would have taken a big step towards qualifying for the 2026 World Cup with victory in the qualifier, held in Guayaquil.
Casemiro was named in the starting XI, returning to the side for the first time since October 2023, and the United midfielder played the full 90 minutes.
In a contest of few chances, the 33-year-old came closest to finding a breakthrough for Brazil, heading wide in the first half and testing Ecuador goalkeeper Gonzalo Valle in the closing stages.
By then Cunha had been introduced from the bench but the Reds’ prospective new signing found little joy against a defence which has conceded just five goals in 15 qualifiers so far.