Republic of Ireland international keeper Elliot is out for the season after suffering anterior cruciate ligament damage in his country's 2-2 friendly draw with Slovakia on Tuesday evening, leaving Darlow in line to play the final eight fixtures of the campaign.
The 25-year-old former Nottingham Forest man can list just one Barclays Premier league game - a 1-0 defeat at West Brom in which he was at fault for the goal - among his two appearances to date for the Magpies, but new boss Benitez is confident he can do the job.
He said: "It's not good news, but you have to concentrate on what you can do. We have to support Darlow.
"Mentally he's right to come in, he's confident and we know he can do it. He's not played a lot of Premier League games, but he has experience in the Championship.
"We have not really done anything extra with Karl. We have another training session today and will keep an eye on him, but he's trained well."
Elliot's misfortune - he will also miss the Euro 2016 finals, where he had a chance of establishing himself as Ireland's number one keeper - struck just two games into Benitez's reign, but he revealed the 29-year-old was taking a philosophical view.
He said: "It was very bad news for us and for him, but I saw him the day after and he was quite confident he'd be back as soon as possible.
"He's very positive and I was surprised because it's a bad time for him. We can do nothing at the moment. We can't sign another keeper - I saw something (reported) that we can, but no we can't.
"We have to wait and support him and hopefully he's back as soon as possible."