Black is set to return from his second red card of the season on Saturday. The 26-year-old midfielder has also picked up six yellow cards so far this season.
“He’s a very good player,” Sergio told Hearts TV. “He has made some mistakes and we’ve been talking with him to be careful with those kind of situations which can be bad for his career.
“Sometimes he’s making an image of an aggressive guy. If you see his record during all these years he’s played in the SPL it’s not so bad. But it seems like he’s an assassin on the pitch. It’s not true.
“You can see his record in the last eight years. It’s not a bad record.”
