Even with Mandzukic's current form he provided an assist to Kean in that Empoli match. Because he is good with headers, you know. He also could've had an assist vs Milan when he set up Bentacur, again with his head. Even when he walks like a ghost he has an impact because of his physical characteristics.
By the way, can you name another one-footed slow CF who provides no aerial threat in any other top team? or in Juve in past 20 years?