The Spanish international is still recovering from an Achilles injury that has kept him sidelined since October 2016 and underwent a ninth separate operation on the issue last week.
Wenger had previously hoped that the 32-year-old would return at the start of 2018 but speaking before the Gunners' Europa League clash with BATE Borisov, the Frenchman admitted that the latest setback meant he would be out until at least February.
"Unfortunately he has to start again from zero," said the Arsenal boss.
"That means if all goes well he has to wait until he can run and after when he starts to run it will be at least six weeks to come back to training. When he will be able to run again I don't know."
Arsenal face BATE in the Europa League this evening, knowing that they have already secured top spot in Group H.