Chelsea midfielder Jorginho felt fatigue was a factor in their defeat at home to West Ham.
Captain for the day, Jorginho argued Chelsea's draw at Champions League opponents Valencia in midweek took a toll.
After Aaron Cresswell scored the only goal of the game, the midfielder explained, "I think we were not clinical, we need to be more clinical when we create the chances.
"We weren't and then we conceded. Then it is difficult."
On whether the Chelsea players were tired after playing Manchester City and Valencia in a busy week, Jorginho added: "Maybe, but we created some chances but didn't score.
"That's the problem."
