Giorgio Chiellini has described playing for Antonio Conte as like "entering another world" due to his demanding methods and compared the Chelsea manager to a "police sergeant".
In an exclusive interview with the Daily Mail, the Juventus star hailed his old boss as one of the best in the world.
But Chiellini, who spent five years under Conte with Juve and the Italy national team, has admitted his intense approach left players exhausted and he was not an easy person to work for.
Conte won the Premier League with Chelsea last season but his position is currently the subject of intense speculation with reports of a fall-out with club bosses and players.
"It is not only in the match with Conte," said Chiellini. "It is all day, every training session. He is like a police sergeant.
"We felt something very special in his atmosphere, for three years with him at Juventus and two years in the national team.
"When you finish training, you are dead. Not tired — dead. You can do it only because you believe in what he does.
"We had 40 days in France and it was like entering another world. You are 100% with him.
"He creates an atmosphere, everyone gives energy to each other. For sure he is one of the very best."