Both were declared out of the NFC South matchup Friday, and defensive end Will Smith (groin) was a limited participant in practice and is listed as questionable.
It will be the third consecutive game Thomas has missed because of a sprained left ankle.
"I'm a little frustrated, but hey, it's coming along," said Thomas, who told the Times-Picayune his ankle is "starting to look like a normal ankle again."
Thomas said he's doesn't want to risk a setback by returning before he is ready.
"Now I'm in the process of seeing where the strength is at," Thomas said. "It's just taking too long."