The other options at centre-back alongside Thomas Vermaelen are Mikael Silvestre or Bacary Sagna, with Denilson likely to cover as the holding midfielder alongside Abou Diaby.
Related ArticlesInjury worries mount for BarcelonaWenger stalls on new dealIbrahimovic ruled out of Nou Camp returnWenger to hold back Walcott at Nou CampArsenal 1 Wolves 0Ramsey: Shawcross should have backed outIt means that Arsenal will travel to Barcelona this afternoon without five players who would normally be guaranteed to start in Song, Cesc Fabregas, Andrei Arshavin, Robin van Persie and William Gallas.
Song had to be substituted during Saturday's 1-0 win over Wolverhampton Wanderers following a groin injury and, while there was hope that he would be recovered in time to face Barcelona, he was unable to train.
Campbell and Silvestre are both in Arsenal's 18-man squad travelling to Barcelona today, as are Fran Merida, Craig Eastmond and Armand Traore.
Arsenal must either win or draw at least 3-3 to progress to a potential Champions League semi-final against Inter Milan after the 2-2 draw at the Emirates next week.
While Arsenal are severely depleted, Barcelona are also without key players, including their first-choice centre-backs Carles Puyol and Gerard Pique as well as striker Zlatan Ibrahamivoc and midfielder Andres Iniesta.
Arsenal squad: Almunia, Fabianski, Bendtner, Eduardo, Diaby, Nasri, Denilson, Merida, Walcott, Eastmond, Rosicky, Traore, Eboue, Clichy, Sagna, Vermaelen, Campbell, Silvestre.