Eto'o is yet to score for Chelsea since his arrival from Anzhi.
Mourinho said: "The player I know and the professional I know, what happened in Russia during the last two years, I didn't know.
"Normally when you are a top player at the top clubs in Europe and you go to the Russian league, the pressure goes down, the motivation goes down, the physical condition comes down and the sharpness goes down. Now he comes back to top European football and he needs time find that sharpness. He is playing a lot and he is getting his form. Players have to adapt to their age and condition."
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