The Ghanaian has been out of action since straining a muscle while attempting a shot in a league fixture with Bournemouth earlier this month.
With the injury initially not thought to be serious, Atsu headed for international duty after the game but a relapse while training with Ghana has sent him to the sidelines.
“[Jamal] Lascelles is getting better, but still he will need some time, and Atsu is the same. It is too early to say [when they will be back],” Benitez said in a player fitness update, as reported by his club’s official website.
“But [Mikel] Merino has been doing part of the training session and [Paul] Dummett has done the full training session, so that is positive news for us.
“I think it’s important to have players coming back.
“With Merino, he was doing so well and the fans were so excited. If he is OK it will be a big boost for everyone, because you always need quality."
Atsu’s injury forced him out of Ghana’s clash with Egypt on November 12 in 2018 World Cup qualifying.
He was also missing as Newcastle faced Manchester United in the Premier League on Saturday, consequently failing to add to his 11 league appearances and one goal for the Toon Army this campaign.
He joined Benitez’s outfit on a permanent deal in June following a season-long loan stint from Chelsea last season.
