The Spanish midfielder, who was initially expected to be sidelined for three months, is aiming for a return to action in March after undergoing surgery on the knee he injured against Norwich City late last month.
"Arsenal have told me it will be between three and four months, which may be closer to four," he told Spanish radio station Cadena Cope.
"I am trying to take it well. These are the things that happen in football and I am trying to recover as soon as possible.
"I have to be ready mentally to work and hopefully I can shorten the recovery time as much as possible.
"I do not want to set a time but I want to play in three months. I do not want to extend it more if it is possible.
"I have already said that I will work hard, I want to make everything I can to play in March but we will see how it goes.
"We are not going to force it if is going to be bad. But my priority is to play in March.
"The club have told me to be calm and that when I return we will be in the finals (laughs). I hope so. The important thing is that the team do well and I recover as soon as possible."