Juan Mata suffered a suspected broken finger during Chelsea's 3-1 loss to Napoli last night.
The Spaniard, who scored Chelsea's goal in Naples, is believed to have suffered the injury following a first-half collision with Napoli defender Salvatore Aronica.
When asked about Mata's complaint, Chelsea manager Andre Villas-Boas told reporters: "We have to check it. Maybe it is broken."
Mata is now expected to undergo a series of tests to determine the extent of the problem.