Chelsea manager Jose Mourinho has admitted that international commitments are likely to rule Juan Mata and Fernando Torres out of his first match back at Stamford Bridge.
The Blues begin their Premier League campaign against Hull City on August 18, but three days before a large majority of his squad will be involved in friendly internationals.
Spain have a trip to Ecuador booked for August 14, with any player involved not due back in London until just 24 hours before the Hull match because of the long flight to Guayaquil.
La Roja boss Vicente del Bosque is expected to call on Mata, Torres and Cesar Azpilicueta for the Ecuador friendly, with Mourinho conceding that the trio will probably not start against Hull as a result.
He told The Guardian: "My lineup will depend a lot on which players go away with their national teams two days before the opening of the Premier League. If one has to go to Ecuador and comes back and arrives in London on Saturday without having slept after a 15-hour flight, coming in to train on Saturday morning, I don't think he is going to play on Sunday.
"If a player plays for England on Wednesday against Scotland, let's say plays for 45 minutes at Wembley and then an hour after the game he is at home in Cobham sleeping, he is in a better condition to play. The team will be decided game after game and week after week.
"What happens before the Hull City game has an impact. Also, if we have to play against Aston Villa two or three days later, we still don't know when that will be. I will have to think about two or three matches at the same time. If the game is postponed until two months later and I have only one match in a week, I will think differently. It depends on the situation."
Chelsea continue their pre-season preparations with a friendly against an Indonesian All Star XI on Thursday.
