The 26-year-old was substituted through injury just 18 minutes into the Gunners’ win over Everton on Sunday, following a collision with Toffees’ defender Djibril Sidibe.
Kolasinac left the field with his arm wrapped in his shirt to provide support, with Arsenal confirming on Wednesday he had suffered a “significant shoulder injury”.
It was Kolasinac’s first game back from a previous injury sustained six weeks prior, and he now looks set for a further spell on the sidelines.
He posted an update to his followers on Instagram , which read: “Thanks for all your messages. Hope to be back soon! Further specialist assessments are needed #shoulderinjury.”
Arsenal have been deploying youngster Bukayo Sakato good effect in the left-back role in the absence of Kolasinac and Kieran Tierney – who is also out with a shoulder injury.
But the news still comes as a blow to Arsenal, with boss Mikel Arteta admitting he is not sure if Kolasinac will play again this season.
Asked at Wednesday’s press conference if Kolasinac would feature again in the campaign, Arteta replied: “Hopefully, yes. But I don’t know.
“It’s depending on whether he’s dislocated it and if he needs surgery or not. We will know more this afternoon, hopefully.
“He is seeing the specialist and we will know more – but yes, he was in pain, it’s a difficult area and we are not very positive about it.”
Kolasinac’s injury could also mean he misses Bosnia’s Euro 2020 play-off semi-final, as he faces a race to be fit for the clash with Northern Ireland on March 26.
Arsenal meanwhile are hopeful Tierney will be back in full training by the end of this month to ease the burden on youngster Saka.