Arsenal are facing a mounting injury crisis ahead of Sunday's showdown with Chelsea following the news that Johan Djourou has joined William Gallas as a doubt for the trip to Stamford Bridge.
The Gunners face their London rivals, live on Sky Sports 1, needing a win to have any chance of keeping their fading title hopes alive.
Gallas has missed the last five games due to a thigh injury, and boss Arsene Wenger has now confirmed that the French international has only a 20 per cent chance of facing the side he left under acrimonious circumstances over the summer.
With Kolo Toure also suspended for the short trip across London, Wenger is lacking his favoured central partnership, but backup Djourou is now also rated as doubtful due to a hamstring injury sustained in Wednesday's 0-0 UEFA Champions League draw with Porto.
Following the game in Portugal, Wenger confirmed that his defensive options are rapidly decreasing.
"We can focus on the game on Sunday now," said Wenger to the club's official website after Arsenal finished top of Group G.
"But Gallas is 80 per cent unlikely to play and Djourou is also a problem because he has a hamstring strain."
Swiss international Philippe Senderos could now be the senior figure at the heart of the Arsenal backline for the London derby and, if Djourou and Gallas both fail to recover, then Wenger could press Gilberto, Alexandre Song or Justin Hoyte into an emergency role.