Manchester City striker
says tests have shown he has torn a hamstring, but gave no indication when he will be fit to return to action.
The Argentina international missed City's 3-0 victory over Watford in the FA Cup third round on Saturday after sustaining the injury late in the 3-0 win over Stoke on Tuesday.
Manager Roberto Mancini initially hoped to have his joint top-scorer back for next weekend's trip to Arsenal, but that looks doubtful after Aguero visited a specialist in Italy.
On Twitter , Aguero wrote on Saturday that "the studies confirmed I have a torn muscle. We have to keep on thinking positive and try to recover in the best way possible."
Aguero has 10 goals for City this season , level with Edin Dzeko .