Brazil trio Oscar, Willian and Ramires, Belgian pair Eden Hazard and Thibaut Courtois, and Germany's Andre Schurrle have all missed the majority of Chelsea's pre-season preparations after featuring at this summer's World Cup.
"Are they ready individually? No," BBC Sport quotes the Blues boss as saying.
"But we have to be ready as a team for Monday. Can it be a team of six guys not ready? No.
"This is modern football. It's going in this tendency - more matches, more competitions, less time to work, even not enough time to have a real holiday for bodies and brains that top football players need. There's not enough time."