The 27-year-old, who will now compete for a spot in United’s midfield, finally joined the Red Devils on deadline day, following months of speculation.
United signed Amrabat on an initial season-long loan deal, though the deal includes an option to purchase the Moroccan.
After failing to raise enough funds through player sales, United had to wait until the final days of the window before making a move for Amrabat.
Matt Hargreaves, United’s head of negotiations, took a private jet to Florence in order to conclude a deal.
There was not enough time for Amrabat to fly to the UK, so a medical was booked for him in Italy.
It was during the medical that staff detected a back issue, according to the Athletic.
The midfielder had to take pain-killing injections during Morocco’s run to the World Cup semi-finals in December.
On the day of the country’s semi-final against France, Amrabat was convinced he would not be able to play due to the pain in his back.
The problem has persisted, and staff detected the issue during the medical.
However, it was not deemed serious enough to block the transfer and United completed the loan deal.
Amrabat could make his debut against Brighton after the international break.
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