The pair have been ruled out of action this weekend, but Victor Moses and John Obi Mikel are available as they will only leave for the Africa Cup of Nations after the game
Defender Terry has been out since November after picking up a knee injury against Liverpool and Chelsea remain unsure as to when the former England captain will return to full fitness.
Cech, meanwhile, is expected to be out for up to two weeks after picking up a groin injury. Ross Turnbull deputised in goal for the club and may do so again on Saturday.
However, Benitez did reveal that Victor Moses and John Obi Mikel are available for selection as they will only join up with the Nigeria squad ahead of the African Cup of Nations after the game.
"Petr [Cech] did a light training session, we will see but it will probably be about two or three weeks, I don't think we will change the estimations now," said the interim manager.
"With [John] Terry, it depends on the reactions, today he did a little bit more with the team. He's closer but we don't know how close, but it's positive because he's training.
"Moses and Mikel have to be there on Saturday, so they can play with us and are available. They have a training camp in Portugal."
Further positive team news for the Blues comes where new signing Demba Ba is concerned, who is fit and available for selection.
The 27-year-old striker completed his move from Newcastle on Friday and could now feature against Southampton.