The 20-year-old has been sidelined by a hamstring problem since limping out of the Champions League clash in Sevilla on November 27, but Wenger revealed there was no guarantee his star man would be back for the visit of Premier League title rivals Chelsea on Sunday.
"We haven´t set any date for his return yet," said the Arsenal manager. "Cesc is not with the group at all; he is with the medical people being treated. He is working very hard. Cesc is very impatient, but he is not back yet."
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