The Dutch international winger, who will miss Wednesday's friendly against England, left Blackburn on crutches on Wednesday night after being injured in a tackle by Aaron Mokoena and he has not walked on the foot since.
"There are no conclusions for the moment," the Chelsea manager, Jose Mourinho, said. "The only conclusion is big, big pain. Arjen can't walk, put his foot on the floor and he is immobilised. The examinations are not conclusive because the inflammatory process is really big. Because of all the blood and fluid showing in the scan, they can't understand yet whether it is a fracture or not, or whether there is damage in a ligament or not."
Blackburn and Chelsea have been charged by the Football Association with failing to ensure that their players conducted themselves in an orderly fashion during Wednesday's game.
Mourinho criticised the scheduling of the next set of Premiership fixtures, which he believes will give Chelsea's rivals extra time to recover following the international matches.
The top three sides' league games will be broadcast live by Sky over three days next weekend. However, while Chelsea must play Everton at Goodison Park on Saturday lunchtime, the Manchester derby does not kick off until Sunday afternoon, while Arsenal have got until Monday evening before they entertain Crystal Palace.
"I have been here for six or seven months so I am still new and there are a few things I don't understand well," Mourinho said. "One of the things is, who is controlling the matches on television and who decides which game is on Saturday, which is on Sunday and which is on Monday? I cannot understand why it is always the same team with the difficult task. Somebody is in charge, somebody is controlling, somebody is deciding and somebody is always giving us the difficult task."Reuse content