The £15million signing from Stuttgart lasted just 45 minutes of his debut against Southampton before suffering an ACL injury.
He has since undergone successful surgery and is already on the road back to a recovery, and Lage is encouraged by his progress.
"The operation was good, I can see him in the building, he is enthusiastic to have the best recovery," the Wolves boss said.
"But it was very disappointing. I have been here 15 months and asked for a striker with a different profile than Raul, to try to find a different profile.
"Sasa is going to be nearer the box and he just played 45 minutes for us.
"I can see him every time he is here in the building with motivation to recover as quickly as possible.
"This type of injury will be six months and then depending on him. At least six more months in front of him."