The Frenchman picked up the problem while on a run in pre-season, and Lambert had hoped that he may return by the end of the campaign.
However, the Scot revealed that the chances of seeing the 27-year-old in action before May are looking increasingly unlikely.
In better news for the Villa boss, however, Jores Okore is back in light training after rupturing a knee ligament in September and Lambert hopes to have the Dane back before the season is over.
"He's still doing rehab," Lambert told The Birmingham Mail. "Charles' injury is probably worse than Jores Okore's was and that's disappointing.
"It will be a big ask for Charles to come back this season because he's not had many games at all and that Achilles heel, as everybody knows, is a major issue."
On-loan Chelsea full-back Ryan Bertrand feels Sunday's 4-1 win over Norwich City was a marker for what the side can achieve between now and the end of the season.
"A win does wonders for the club," he said.
"We're in an okay position now so we have to keep focused and keep it going for as long as we can.
"We've had a mixed bag of results but it's important that we've been able to get a good win just before the break and hopefully we can take that into the next game."
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