كتب : Ahmad Saied
Ferrara's side slumped to a 2-0 defeat against Cagliari, leaving Inter eight points clear at the top of the league table.
And the Juve coach had put question marks over Diego's commitment to his side's cause after the game.
"He has the desire to play many balls as a characteristic and so he often retreats, tracking back to get them," Ferrara said.
"But he also has to work on the aspects asked of him by the trainer. I am sure that he will improve.
"Diego is a great player. I will continue to spur him on until he gets closer to goal and becomes decisive there," he added.