Chelsea vs Aston VillaDidier Drogba's knee injury rules him out of Chelsea's Barclays Premier League clash against Aston Villa at Stamford Bridge.The striker joins Deco (thigh), Ricardo Carvalho (knee) and Michael Essien (knee) on the sidelines.Ashley Cole (back), Joe Cole (hip), Alex (buttock) and John Terry (back) all are hopeful of being fit but may require late checks.Luiz Felipe Scolari has insisted Chelsea's squad is big enough to mount a title challenge, although he admitted his prayers