Returning Real Madrid manager Zinedine Zidane has reportedly fired a warning to goalkeeper Thibaut Courtois over his poor form.

Courtois's future in the Spanish capital is believed to be in doubt following this week's reappointment of Zidane, who previously blocked the club's attempts to sign the Belgium international from Chelsea.

Zidane's departure last summer coincided with Real finally striking a £38m deal with the Blues, but the 26-year-old has failed to replicate the type of performances shown at Stamford Bridge across his first seven months at the Bernabeu.

According to a report carried by The Sun, Courtois has been told to up his game or else he risks losing his place between the sticks to Keylor Navas - the most used player still at the club during Zidane's first two-and-a-half-year reign.

Real have conceded 32 goals in 27 La Liga games this season, 24 of which Courtois has started.