Arsenal centre-back Rob Holding has been ruled out for up to nine months after he ruptured the anterior cruciate ligament in his left knee on Wednesday.
Holding had made 16 appearances for Unai Emery’s side this season.
“Rob will undergo surgery in the coming days and rehabilitation is expected to take between six to nine months,” said an Arsenal statement.
“Everyone at the club will now be working as hard as we can to ensure Rob is back on the pitch as soon as possible.”
“Gutted to get injured during a strong period for the team!” said Holding, who also added his thanks to “all the fans, players and staff members for the support during the past couple of days”.
Holding underwent tests in London following the collision with United’s Marcus Rashford nine minutes before half-time.
The injury is the latest defensive setback for Arsenal, who remain without centre-back Laurent Koscielny and left-back Nacho Monreal.
The Gunners, who are unbeaten in their last 20 matches in all competitions, dropped down to fifth in the table after their 2-2 draw at Old Trafford.
They host Huddersfield in the Premier League on Saturday.