Chelsea will be without central defender Ricardo Carvalho for up to eight weeks.
He suffered a back injury in last weekend's 1-1 draw with Everton, and scans revealed damage to his spinal column.
Portugal team doctor Henrique Jones confirmed the blow, and explained the extent of the problem.
"Ricardo has suffered fractures of the small bones on his second, third and fourth vertebrae and will be out for eight weeks," he said.
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The news will come as a major blow to Chelsea manager Avram Grant, who already has Petr Cech, John Terry and Paulo Ferreira sidelined.
