The progress of the Sweden Under-21 international, who had a successful loan at Feyenoord two years ago, has been blocked by injury and illness.
Pellegrini said: "I think John must go on loan, he is coming back from a long injury for about 18 months.
"Here we have (Edin) Dzeko, (Alvaro) Negredo, (Sergio) Aguero and (Stevan) Jovetic. Maybe he will not play as often as he needs so maybe it is best for him and the team."
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