Mark Reynolds has been called into the Scotland squad for Sunday's European qualifier in Germany.
The uncapped Aberdeen defender has been drafted in as cover for Ipswich's Christophe Berra, who is being treated for an injury and has not yet joined up with the squad.
Celtic's Charlie Mulgrew is also receiving treatment on a knock but is expected to train later in the week ahead of the trip to Dortmund.
Gordon Strachan's assistant Mark McGhee said: "Christophe is being looked at by his club but we are still hoping that he will show. We have brought in Mark Reynolds as a precaution in case he doesn't.
"Mark was unfortunate not to be in the squad in the first place, he is certainly one of a short list that could have been in the squad. We know him, he knows us, so it is easy.
"Charlie is here. He won't train in the early part of the week but we expect him to be available for selection."