Manchester City defender Benjamin Mendy faces a long spell out after tests confirmed he has ruptured the anterior cruciate ligament in his right knee.
A serious problem was suspected when the France left-back suffered the injury during the first half of last weekend's 5-0 victory over Crystal Palace.
After initial tests in Manchester, Mendy travelled to Barcelona to see a specialist, where the extent of the damage was confirmed.
City splashed out £52million to bring Mendy to Manchester from Monaco during the summer.
The 23-year-old missed the first two games of the season with a thigh problem before making his debut in the 2-1 win over Bournemouth on August 26.
Mendy then played in the games against Liverpool, Feyenoord, Watford and Palace, with City keeping clean sheets in each one.
A statement on City's website read: "Benjamin will undergo surgery tomorrow (Friday) in Barcelona, and everyone at the club wishes him a speedy recovery."
Mendy appeared to take the injury setback in good spirits, tweeting: "Bad news guys ll be joining Injury FC on loan for a couple monthes with ruptured ACL... but will be back soon & stronger hopefully."
Also, when asked on his social media account about his 'FIFA18 One to Watch Card', the Frenchman responded: "Sell it asap"
City take on Chelsea in a huge early-season game on Saturday. Sky Bet currently make them 7/5 favourites.
