Club sources have played down the seriousness, insisting it is a precautionary, minor corrective procedure to rectify a relatively common condition.

Mazraoui has suffered heart issues previously – after testing positive for Covid during the 2022 World Cup he was diagnosed with a mild inflammation of the pericardium (the membrane surrounding the heart) a month later – but the PA news agency understands there was no suggestion of an emergency situation ahead of this latest procedure.

United have not put a timescale on his return and expect him to be available for selection “in the next few weeks”.

The defender, who pulled out of Morocco’s squad on Monday, joined United from Bayern Munich for £12.5million in the summer.