Chelsea's defensive options have been further limited by the loss of Ricardo Carvalho with an ankle ligament injury.
Alex will deputise in a defence now shorn of four regular starters. Midfielder Michael Ballack returns from an Achilles complaint.
Aston Villa have fitness concerns over a quartet of key players.
Gabby Agbonlahor could miss out for the third game in a row with a toe injury, while Richard Dunne, James Milner and Emile Heskey have Achilles problems.