Fabio Capello says Antonio Conte and Jose Mourinho's feud has spiralled out of control, and that the Chelsea coach would have been wise not to have picked such a fight.
Conte and Manchester United counterpart Mourinho have exchanged jibes in recent weeks with tension building ahead of their meeting on Feb. 25 at Old Trafford next month.
Capello has followed the argument and admits he is shocked at how far it has gone, though insisted Mourinho has history in this regard.
"I think Conte didn't realise who he was up against," Capello told Sky Sport Italia. "It's the Chelsea shirt which winds coaches up. Remember how wound up Mourinho got when he was Chelsea manager? Conte's just doing what Mourinho used to do.
"We all remember Mourinho on his knees in the middle of the field, running wild after his side won.
"They're completely out of their minds. I never thought it could get this far. But remember, when you wind Mourinho up, he's very clever in these debate situations. Maybe once again he just wants to divert the attention from his team."
Capello says he would never have confronted Mourinho in such a way, particularly since he would not have been confident that he would have been able to find the right words.
"You've got to have a very good grasp of English," he said. "I would always want a trusted interpreter with me because your words in English could be interpreted in a different way. But confronting Mourinho is very dangerous.
"I think Mourinho is getting a bit nervous. I know him very well. The gap [between United and City] is very big and this can make him nervous. But I've got to say that Manchester City have been spending £200-250 million every year. In the end, they're bound to build a decent side."