The duo made the move to Stamford Bridge during the summer transfer window from Russian club Anzhi Makhachkala.
Striker Eto'o and Brazilian forward Willian are still to make their debuts for Jose Mourinho's men, with Terry revealing that the pace of preparation at Stamford Bridge is above what they are used to.
The Blues will look to continue their unbeaten start to the season when they tackle Everton at Goodison Park on Saturday evening, live on Sky Sports 1HD.
Terry told Chelsea TV: "You speak to them and they talk about how the intensity of their training is a lot different to how it is here so for sure it will take them a few weeks to get their full fitness.
"But once they do they'll both look very good. I said to him (Eto'o), 'Thank God you're here', because I've had so many battles against him.
"He's such a threat, he's obviously a few years older but he still looks very sharp and hungry.
"He's got an eye for goal and I think he'll be a good addition. He was welcomed straight into the squad."