Wagner gave the latest update on the injured Chelsea loanee, who had been expected to be out until the new year, at a press conference before Tuesday night's Carabao Cup tie at Crystal Palace.
Palmer suffered a recurrence of an old hamstring injury while on recent international duty with England Under-21s.
"There have been further discussions now between Chelsea's medical department and our medical department and another neutral specialist as well," Wagner said.
"So he has an injury, a serious injury, maybe not as bad as we thought in the beginning, but I don't expect him back before six to eight weeks.
"It makes no sense now, where he has so many setbacks with his hamstring, always the same one, to rush something
We need him back consistently."
Wagner also confirmed Collin Quaner will be sidelined for between 10-14 days due to a calf injury sustained in training and that fellow striker Steve Mounie will not travel as he is still struggling with a heel problem
Joel Coleman will return in goal having replaced first-choice Jonas Lossl in Town's 2-1 win against Rotherham in the second round, but Wagner gave nothing else away as to other possible changes
The Terriers stunned Palace with a 3-0 win at Selhurst Park on the opening day of the season, but Wagner laughed off suggestions his side are favourites to reach the fourth round of the competition for the first time in nearly 18 years.
"We've beaten them, but this doesn't mean we have to do it again," he said
"This doesn't help you, that you have beaten them.
"It's an open game
We'll try everything to be successful
Maybe, because of the changes they have done on the manager position, there will be a bigger difference in their game."
Wagner said he was looking forward to crossing swords with former England boss Roy Hodgson
Hodgson, 70, lost his first game in charge of Palace 1-0 at home against Southampton on Saturday after replacing the sacked Frank de Boer four days earlier
"The last time I met him I sat on the bench for Schalke in 1997 in the final of the UEFA Cup and he was the manager of Inter Milan," Wagner added.
"I'm not sure he knows I was on the bench
I know he was the manager of Inter
I was too small
I was no name he would recognise I'm sure.
"It's a very good memory because we won on a penalty shootout
No surprise, probably
But it was a long time ago."
Source : PA