Graham Dorrans is the latest player to withdraw from Scotland’s squad for the European qualifier against Germany.
Scotland manager Gordon Strachan also saw defenders Christophe Berra and Andy Robertson pull out of his squad on Wednesday.
Strachan believes Dorrans’ injury is not a serious one, suggesting rest and recuperation will see the West Brom midfielder back in action soon.
“He’s been playing with an injury the last couple of weeks,” Strachan said. “It was great that he came up here and gave it a couple of days rest and tried to train but he was not comfortable.
“So he’s away back now to get assessed from his physios and doctors. They know what it is. I think it’s just about rest but you need to ask them exactly what they’ve got to do and how long it’s got to be.
“All we know is he came up and gave it a right good shot to try and get himself fit and included in the team.”
Strachan confirmed that Darren Fletcher will be his captain. Scott Brown wore the armband during Fletcher's long absence through illness, but the Celtic midfielder is out with a hamstring problem.
He added: "It's great to have his enthusiasm and his experience. You can tell the players enjoy him being here and
more so he enjoys being here."
Sunday’s game in Dortmund will be the world champions’ first competitive international since their World Cup win in Brazil this summer.
Joachim Low’s men were in action on Wednesday night in a friendly against their World Cup final opponents Argentina.
But they slipped to a 4-2 defeat in Dusseldorf after goals from Sergio Aguero, Erik Lamela, Federico Fernandez and Angel di Maria gave the visitors an emphatic lead.
Chelsea’s Andrea Schurrle and Bayern Munich’s Mario Gotze were on target for Germany.
Watch Scotland's European Qualifier away to Germany live on Sky Sports 5 HD on Sunday, with coverage underway from 7.15pm.