The 23-year-old French worldwide, signed for £50 million ($67 million) from Monaco in the summer, will undergo surgery in Barcelona on Friday on the injury he suffered in last weekend's victory over Crystal Palace.
But now, after hearing that he has ruptured his anterior cruciate ligament, he's maintained his playful online persona and made fun of his strife.
City's medical team had initially hoped he had only sustained an impact injury, but ESPN FC reported on Tuesday that he would be sent to see specialist Dr Ramon Cugat in Barcelona.
Benjamin Mendy to have surgery on ruptured knee ligament
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".
"Benjamin will undergo surgery [Friday] in Barcelona, and everyone at the club wishes him a speedy recovery".
The news poses huge problems for Guardiola, who is now without a dedicated left back.
The City boss also did not rule out buying a new left-back in the January transfer window after being linked with Southampton's Ryan Bertrand over the summer. City's midweek match against Shakhtar Donetsk saw Fabian Delph fill in Mendy's position, and the only other suitable option ahead of the club's weekend encounter with Chelsea comes in the form of natural right back Danilo.