Ranieri said: “It's difficult to win the league the second year. Chelsea also has the Champions League and then it's not easy.
“It's not easy when a lot of other teams are renovating their players."
Over the summer, more than £100 million was invested in the squad signing Alvaro Morata, Tiemoue Bakayoko and Antonio Rudiger after the departure of Nemanja Matic, who was sold to title rivals Manchester United and Diego Costa, who moved to Atletico Madrid.
“He is happy. He is a fantastic manager and tries to do the best for Chelsea," he added.