Roy Keane was stunned by a piece of defending from Tyrell Malacia (Picture: Getty Images)

Roy Keane couldn’t believe what he was seeing from Tyrell Malacia during Manchester United’s FA Cup clash with Reading on Saturday night, saying what the full-back was doing ‘drives him crazy’.

United hosted Reading in the fourth round of the FA Cup, with the Championship side looking to cause a big upset at Old Trafford.

The first half was dominated by the Red Devils but the best chance of the half fell to Reading’s Junior Hoilett thanks to a mistake from Malacia.

The United left-back wanted an age to control the ball in his own penalty box, taking it down on his chest before trying to clear but Hoilett pounced and poked a shot at David de Gea from close range.

The Royals man didn’t make a great contact and it was pretty comfortably saved by the Spaniard, but Keane was stunned by the piece of defending.

‘What are these defenders thinking? Honestly, it drives me mad. As if he’s surprised somebody’s next to him!’ Keane fumed on ITV.

‘Switch on! Be aware of what’s next to you on the football pitch. It drives me crazy.’

With the game still goalless at half-time, there was a bit of edginess at Old Trafford, but that was quelled in the second period as they asserted their authority.

By the time the hour mark had passed the Red Devils were 2-0 ahead thanks to a double from Brazilian midfielder Casemiro, who produced two very different but equally superb finishes.

There was more joy for United fans as former Liverpool striker Andy Carroll was shown a red card before Fred made it 3-0 and put the game to bed.

Amadou Salif Mbengue nodded in a consolation from a corner for Reading, but that’s all it turned out to be for Paul Ince’s side.

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‘What are these defenders thinking?’