Manchester United manager Michael Carrick says Matthijs de Ligt’s recovery from a back injury is progressing slower than expected and he has no idea when the Dutch defender will be able to return to action, Reuters reported. 

De Ligt, 26, has been sidelined since United's 2-1 win over Crystal Palace in November and there are doubts he will be fit for the World Cup, which starts on June 11 in North America.

"It's one of those things with backs that, sometimes, you think it's alright and then, all of a sudden, it's not quite right," Carrick told reporters on Thursday, according to Reuters.