The duo first played together at Real Madrid in the 1990s and reunited at Russian outfit Anzhi Makhachkala in 2011.
"I've known Eto'o since he was 16. He's a good person and I've always liked him, but he always thinks of himself, not the group," Carlos told Globoesporte.
"It's quite confusing and odd when a footballer, instead of playing, is interested in bringing in players who are his friends. He did everything at Anzhi, except play football. There were a few small problems in the dressing room with the arrival of Eto'o, which were resolved.
"His signing had to be explained to several players. Then there came a point when Samuel wanted to interfere in my work. He wanted to control the club, taking my place and that of the coach, Guus Hiddink."
Eto'o joined Chelsea towards the end of the summer transfer window.