Martin Keown is concerned about Unai Emery’s lack of defensive options .
The visitors took advantage of the Gunners makeshift defence to claim a 3-1 win at the Emirates.
Arsenal centre back Sokratis was forced to hobble off the pitch with the game still goalless.
And just 10 minutes later Romelu Luakaku ruthlessly exposed hesitancy in the home side’s defence to give United the lead.
Attack then became the best form of defence for Arsenal who have already lost two defenders to season-ending injuries.
Long-term absentee Rob Holding was joined by Hector Bellerin who ruptured his ACL against Chelsea last weekend.
The Gunners fell for a Jesse Lingard sucker punch to go 2-0 down before pulling a goal back before the break.
Pierre-Emerick Aubameyang was in the right place at the right time to tap home his 17th goal of the season.
But Gunners boss Unai Emery was soon cursing his luck again as captain Laurent Koscielny took a boot to the face.
Lukaku accidentally kicked the Frenchman in the face and appears to have broken his jaw.
And Arsenal hero Martin Keown thinks the worsening injury crisis could force Emery’s hand.
He wrote in the Daily Mail: “Emery admitted earlier this month that he would only be able to bring in players on loan.
“This FA Cup exit may force Arsenal into the transfer market for a defender.”
And he admitted he has sympathy for Emery’s plight in his first season as Arsene Wenger’s successor.