The Chelsea striker says his manager can become a different person in the buildup to matches.
The Blues boss oversaw an impressive 6-0 win over Arsenal on Saturday, which pushed the club four points clear at the top of the Premier League table.
But Mourinho was caught out earlier this season, as he appeared to call Eto'o old during a sponsor's event in Nyon — and was unaware he was being filmed.
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But the Cameroon striker has now put the jibe down to Mourinho putting too much pressure on himself.
"He becomes someone else in the buildup to matches,” he told beIN Sports. “Like any human being, he sometimes loses his mind.
"He proved it sometimes like when he did it with me [by calling me old] but he takes all the pressure on himself.”
Eto'o also discussed his fallout with former Barcelona boss Pep Guardiola, who he claims wanted to send him to Uzbekistan.
The pair argued during their time at Camp Nou and Eto'o believes he was shown a “total lack of respect” by the Spaniard, who often used Thierry Henry ahead of the current Blues star in the starting lineup.
“Guardiola has never been a great player, he was just a good player. I told him. He didnt prove anything when he arrived and he said certain things,” Eto'o said.
“What hurt me is that they invent things that the press relayed. They wanted to send me to Uzbekistan. I stayed at my place and I told him that he will apologize for that in the future.
“He gave the number 9 to Henry. Henry was happy. And it was a total lack of respect. I had done a lot for the club. Guardiola has never had the courage to say things in front of me. He passed by the players. Xavi told me they wanted me to stay but I had to talk to Pep. I say, 'Never. If you do not respect me, I do not respect you.'
“He shook hands with me when I was at Inter and I played against Barca, but this was just for the cameras and TV. Behind the scenes before the match, he did not greet me."