Rafael Benitez has admitted he can be not very nice when he is angry, but insists he has moved on from his feud with Jose Mourinho.
The two men, who have both managed Chelsea, Inter Milan and Real Madrid, go head-to-head on Saturday, this time when Benitez takes his Newcastle team to Old Trafford to face Mourinho's high-flying Manchester United.
They have not met in the Premier League for more than 10 years but the rivalry which brewed between them during their spells in charge at Liverpool and Chelsea, respectively, sparked a war of words with the genial Spaniard twice dumping the Blues out of the Champions League.
However, asked if he is older and wiser now, Benitez said: "I think so. Older -- that is obvious -- and a lot calmer and more relaxed, because you have more experience.
"You know what's important. The main thing is the players. You have to concentrate on that. You have to be sure you get the best from your players.''
Benitez, who also famously tangled with former United boss Sir Alex Ferguson during his time at Anfield, presents an affable front, but he is not afraid to bare his teeth when he feels the need to.
He said: "As a manager, you have to make decisions to leave players in the stands or say something that you think is good for your team.
"Normally, I try to be respectful to everyone and do the best for my team.''
But asked if he was not nice at times, he replied: "Yes, for sure, when I am upset. I try to be respectful to everyone, but sometimes I'm upset and I'm not [nice].''
Newcastle will run out having lost their last two games -- to Burnley and Bournemouth -- and knowing they face a major challenge to address that this weekend.
However, were they able to win, Benitez would become the manager to taste Premier League victory at Old Trafford with three different clubs.
He said with a smile: "Hopefully we can say that, but for now we stay calm and focus on it.''