Rangers winger DaMarcus Beasley will be out of action for three weeks with the hamstring injury he suffered in the 1-0 friendly win over SC Preussen Munster.
The American is now set to miss the Champions League qualifers against either FBK Kaunas or Santa Coloma.
Beasley, 26, missed six months of last season with knee ligament damage but returned to the first team in May.
"Hopefully it is not too long but he will miss the remaining matches in Germany," said manager Walter Smith.
Meanwhile, assistant boss Ally McCoist and coach Ian Durrant will travel to Andorra to watch the first leg of Santa Coloma's tie with Lithuanian side Kaunas.
McCoist and chief scout Ewan Chester will take in next week's return leg in Kaunas.
"Andrius Velicka will get involved in training this week""Kaunas have changed their side a little bit," Smith added on the club website.
"I saw them last week and if they do go through they will be an awkward team to try to overcome because they are strong physically.
"Their Brazilian player Ledesma is the one who can do something a little bit different for them.
"He is really good at set pieces and we will need to watch that. The game I went to watch was settled on one of his set pieces."
Charlie Adam scored the only goal of Rangers' win over Munster from the penalty spot and former Hearts and Kaunas striker Andrius Velicka may feature in the Ibrox side's upcoming friendlies against German sides Sportfreunde Lotte and Schalke.
The Lithuanian completed his £1m move from Viking Stravanger on Monday and will join the squad at their training base in the Netherlands.
"He didn't play in the last couple of games for Viking but that might be that they were making sure he didn't suffer any knocks before coming to join us," said Smith.
"We will let him get involved in training this week and then make a decision on whether we use him in the remaining matches here."
Another of Smith's summer signings, Kyle Lafferty, and defender Carlos Cuellar missed the Munster match with minor knocks but both are expected to make quick recoveries.
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