Casemiro believes Manchester United are capable of 'achieving great things' under Erik ten Hag and has backed him to turn his team's fortunes around.
The Dutchman led United to a third-place finish in the Premier League last season and won the Carabao Cup, the club's first trophy in six years.
But United have failed to build upon a promising showing in ten Hag's first season in England and have badly regressed badly this term, putting his job under scrutiny.
United are eighth in the Premier League, 11 points behind fourth-placed Aston Villa, and have already lost nine times in 21 league games.