Foster has revealed that intensive English lessons are beginning to bear fruit.
"Claudio has done great," he told the Birmingham Mail. "He is having hour-long lessons every day so his English is improving, because he was awful when he first came.
"Him and Youssouf Mulumbu when they were playing together regularly were fantastic.
"They offer so much protection to the team defensively, and going forward he is so calm on the ball, everyone feeds off that and it raises the standard of everyone else. He has been a big miss for us."