The Cameroon international struggled on his debut in Saturday's 1-0 defeat at Everton, prompting critics to claim he had lost his sharpness after two lucrative seasons with Russian side Anzhi Makhachkala.
But Mikel is confident that Eto'o will soon display the type of form he showed during his successful spells with Barcelona and Inter Milan.
"Samuel is a great player, a fantastic player. You could see the way he played, he created some fantastic chances," Mikel said. "That is why the manager brought him in. Obviously he has a lot of trust and belief in him.
"Let's wait and see, the English league is very difficult to adapt to and this was the first game for him and he has done pretty well.
"Chelsea was my first real professional club and it took me six months to a year to adapt, but I think someone like Eto'o, who is well experienced and has played in so many leagues, won't take very long.
"I think he looked a bit sharp so it won't take him long to get back into his fitness.
"He is a world-class player, a fantastic guy. We just have to keep playing with him and helping him to adapt to the Premier League.
"He tries to give his experience so we have to keep working with him, keep playing with him and trying to help him to fit in."
Mikel also played down the defeat at Goodison Park and found encouragement in the number of chances Chelsea created.
"It is about how we bounce back. Sometimes when you know what you've done wrong it is easy to bounce back," he said.
"We need to go back to training and try to find out what we didn't do - although everyone knows what we didn't do, we didn't score goals."