Juventus coach Ciro Ferrara admits Diego is ignoring his instructions.
After defeat at Cagliari, Diego spoke out against Ferrara, saying it was up to him to sort out their problems.
"He has the desire to play many balls as a characteristic and so he often retreats, tracking back to get them," Ferrara said of the Brazilian.
"But he also has to work on the aspects asked of him by the trainer. I am sure that he will improve.
"Above all in the first half I encouraged Diego to try and find more penetration. It has not been his problem alone, but also that of Marchisio, for example.
"Diego is a great player. I will continue to spur him on until he gets closer to goal and becomes decisive there."