Manchester City midfielder Fernandinho has been ruled out for two weeks with the muscle injury that prevented him from playing in Monday's 1-0 defeat to Chelsea.
And manager Manuel Pellegrini insisted he had no choice but to play defender Martin Demichelis in midfield as he insisted City's injury list limited his options and meant he could only make one substitution.
City were without Sergio Aguero, Samir Nasri and Javi Garcia as well as Fernandinho, while the Chilean claimed Alvaro Negredo, who was substituted, and James Milner and Jack Rodwell, who were unused replacements, were not fully fit.
And he suggested Brazil midfielder Fernandinho could be a doubt for the FA Cup rematch with Chelsea on Feb. 15.
He said: "He has a muscle injury. It will be a couple of weeks [out]. He is a very important player for us. Jack Rodwell is coming from an injury for one month. James Milner just worked with us the last day and is not 100 percent.
"The only option I had was Demichelis. That is why Fernandinho's injury was so important, I had to change the defence."
Pellegrini said City's injury problems handed Chelsea the advantage as City, who had won all 11 of their previous home league games, were beaten at the Etihad Stadium for the first time by English opposition this season.
He added: "It not only him [Fernandinho]. Aguero, Nasri and Javi Garcia [were out]. Milner was not 100 percent, Negredo was not 100 percent. It was too much [of an] advantage for an important team like Chelsea [to have]. I put all the players that were in the condition to play [on the pitch], that is why I did not make the other two changes."
Pellegrini insisted it was a must-win game for Chelsea, not for his side, who are now level on points with Jose Mourinho's team.
He explained: "For Chelsea it was a decisive game, not for us. If we had won, we [would have been] six points ahead of them."