Former Manchester United first team coach Rene Meulensteen believes Raphael Varane and Casemiro no longer possess the physical capabilities to thrive in the Premier League.
The Red Devils have endured a difficult start to the season, losing six of their 11 games across all competitions to ramp up the pressure on Erik ten Hag.
Several players have looked short of the form that saw United win the Carabao Cup and finish third in the Premier League last term.
Meulensteen, who coached under Sir Alex Ferguson between 2007 and 2013, has picked out Varane and Casemiro as two players that are struggling badly, and he is not convinced either will be able to turn things around due to the physical demands of England's top flight.