Benitez believes that his squad do not have enough strength in depth to cope with playing a game every three days this month despite costing nearly £300m to assemble.
Chelsea have made just a single signing during the current transfer window, bringing in striker Demba Ba from Newcastle United.
The interim Blues boss told reporters: "We cannot rest too many players because our squad is not that big in certain positions.
"I had a good conversation about this with the owner the other day. I gave my opinion, he listened to me. But I have to concentrate on the team. I have to play Frank Lampard and Ramires all the time because we have problems with injuries and suspensions and we have two players at the Africa Nations Cup.
"We have had nine games a month since I came here and the players are a little tired. You can really see the difference when players are allowed to have a rest."
Chelsea continue their hectic January schedule with an FA Cup tie against League One outfit Brentford on Sunday afternoon.