The ex-Chelsea and Arsenal midfielder signed for Anzhi in a permanent deal last week.
"I chose Anzhi above all for Eto'o," said Diarra.
"For me, Samuel is like a big brother.
"For me it is a new challenge. In Russia just for the money? No, absolutely not. During my career I played for some of the most prestigious teams in Europe, winning many titles, so I think I have been paid enough."