New Chelsea manager Maurizio Sarri warned it could take his new side two months to reach their potential, despite starting the season with a comfortable 3-0 win at Huddersfield Town
Eden Hazard and Olivier Giroud were among the substitutes after their World Cup involvement.
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"The situation until now has been very difficult," said Sarri, whose side lost 2-0 to Manchester City in the Community Shield on Sunday.
"On Monday four players from the World Cup arrived [in training]. And then on Tuesday another two, so it's not been easy for me at the moment."
Asked how long it would be before they were playing at their best, the former Napoli manager answered: "It depends on me and the players. I don't know. Hopefully two months and not three.
"I have to know the characteristics of the players. I have to adapt myself to the characteristics of the championship and the players. Now I study my players."
Watch highlights of the match below;