Arsenal midfielder Jack Wilshere has been ruled out for around three months after successfully undergoing surgery on his left ankle, the Gunners have announced.
The England international was substituted during the second half of Saturday's defeat to Manchester United after damaging ankle ligaments and was subsequently sent to a specialist to be assessed.
Wilshere has now gone under the knife and is likely to be out of action until February.
An Arsenal statement read: "Jack Wilshere has had successful surgery on his left ankle and will be out for approximately three months.
"An assessment with a specialist confirmed the need for an operation and the 22-year-old had successful surgery to his ankle in London on Thursday afternoon."
Wilshere also confirmed the operation went well, thanking renowned consultant trauma and orthopaedic surgeon James Calder, while also expressing a message of positivity on his Instagram account.
He also said his situation was put into perspective by the death of Australia cricketer Phillip Hughes yesterday, two days after he was struck on the neck by ball while batting.
Wilshere wrote: "Ankle needed surgery in the end, went well thanks to the main man James Calder! Work hard for what you want because it won't come to you without a fight.
"You have to be strong and courageous and know that you can do anything you put your mind to. If somebody puts you down or criticizes you, just keep on believing in yourself and turn it into something positive."
He added: "Puts life in perspective when you things like this happen, and makes my injury look like nothing! Thoughts are with Philip Hughes family. Horrible news! RIP."
Wilshere was replaced by Santi Cazorla in the 55th minute of Saturday's game at the Emirates Stadium after sustaining the injury following a sliding challenge by United defender Paddy McNair.
The England man sat out Wednesday's Champions League win over Borussia Dortmund, which saw Arsenal secure their place in the last 16.