Sheffield United midfielder John Fleck will miss Scotland's November internationals with a back problem.
And a groin injury may mean Liam Cooper is also absent after the defender pulled out of Leeds' match with Wolves.
Scotland travel to Serbia for a European Championship play-off final on 12 November.
That is followed by Nations League matches in Slovakia and Israel.
"It's another unfortunate injury," Blades boss Chris Wilder said of Fleck, who is expected to be out for four to six weeks. "He suffered one of those you don't get 99 times out of 100.
"To land on such a small place on his back to do the damage that he has done is so unlucky."
Wilder is already without defender Jack O'Connell, while striker Lys Mousset has yet to play this season and left-back Max Lowe's Premier League debut was cut short on Sunday after he suffered a concussion.
Forward Oliver Burke was only fit enough for an unused spot on the bench in the 1-1 draw at home to Fulham after pulling out of the Scotland squad this month with a knock.
"We are being tested a little bit and can do without that," added Wilder.
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