The midfielder, who signed in the summer from Chelsea for £65million, has started both of his new club’s Premier League matches so far but picked up the issue in the defeat to Tottenham.
Mount came off for Facundo Pellistri with five minutes remaining in north London in what appeared to be a regulation tactical change.
A statement read: “Mason Mount is set to miss Saturday’s game against Nottingham Forest due to an injury picked up in last weekend’s encounter with Tottenham Hotspur.
“The small complaint is expected to keep Mount out until the international break next month.”
Mount, 24, is therefore also a doubt for England’s Euro 2024 qualifier away to Ukraine in September and the friendly against Scotland at Hampden Park three days later.