Luke Shaw
Shaw came off the bench in the 4-1 win over Burton Albion in September. Getty

Former Manchester United defender Rio Ferdinand believes Jose Mourinho is testing Luke Shaw to see if he has the mentality to succeed at the club.

Shaw has struggled to hold down a first-team role under the Portuguese with an injury curtailing a brief run in the starting XI last May. The former Southampton starlet is fit once again but has managed just one appearance for the first-team this season, coming off the bench in the Carabao Cup third round victory over Burton Albion.

He was subsequently left out of match day squads for clashes against Southampton, CSKA Moscow and Crystal Palace with Mourinho suggesting after the victory over the left-back's former club that he is still some way off being ready for a permanent return to the starting XI.

While Shaw's struggles to stay fit have not helped his chances, Ferdinand believes Mourinho is also looking for a response from his player, one that definitively proves to him he is up to the challenge of playing for the club.

"It looks like he is testing them mentally," Ferdinand told BT Sport. "Hit them with something – are you going to stay down or are you going to get up and fight? If you get up then he says yes, that is the type of man I want in my team.

"As players, that is what you want in your team. You don't want players who will get one hit and shy away from things. One bad pass in a game, shy away from taking the ball again for the next 10 or 15 minutes... that is not how you win titles. "You need players who are going to be brave receiving the ball, not just physically but mentally and saying whatever happens here going forward, I will be with you guys shoulder to shoulder."

Shaw signed a four-year contract at Old Trafford after arriving at the club from Southampton in 2014 that will expire next summer. But like most contracts the club have handed out in recent years, United have the option to extend that deal until 2019 with various reports recently suggesting that step has already been taken.