The Spaniard, who has not featured for the Gunners since October 2016, underwent a ninth operation on his achilles last week.
The future looks dark for the midfielder, who is out of contract at the end of the season.
Wenger had hoped to have the 32-year-old back in training in January, which would have provided a timely boost if Mesut Ozil and Alexis Sanchez both leave the Emirates Stadium.
But Cazorla’s comeback has now been postponed for the foreseeable future.
“I sent him a message because he had a new surgery and wished him well,” Wenger told the Evening Standard.
“He answered ‘look I have to start again, from zero basically’ and it is very sad, honestly.
“What he has gone through this guy is unbelievable.
“We speak about players being happy or not happy, that is a real pain because it is really, really sad but unfortunately he has to start again from zero.
“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.
“I was hopeful of January but after, he had this setback that everybody knows about.”
Arsenal here in Europa League action against Bate tonight (8.05pm).