The Brazilian had to be carried off the field after the final whistle of the Carling Cup semi-final against Derby last month and, although X-rays confirmed there was no break, he did suffer ligament damage that has prevented him from training.
He is continuing rehabilitation work in the gym but seems unlikely to be involved in either leg of the UEFA Champions League encounter with Inter Milan.
"Anderson is coming along slowly," confirmed assistant manager Mike Phelan.
"He is working with the medical team at the moment and will start on the conditioning side next week.
"He is making the progress that we expect him to make. It is just a question of how quickly that comes on once he gets out onto the training pitch.
"We haven't put a timescale on it because he is working more inside than out. Once we get him onto the grass we will find out how long."