Sels deleted his Twitter account after being abused online after the club’s 1-1 draw against Aston Villa at the weekend.
The goalkeeper is still adjusting to the physicality and intensity of the Championship after his summer move from Belgian club Gent.
Some fans felt he should have done better for Villa’s late equaliser.
United manager Benitez must now decide whether to persevere with 24-year-old Sels – or hand Darlow his first league start of the season.
Benitez, however, is confident the online abuse has not affected Sels.
“He’s ok and training well,” said Benitez.
“He was working with Simon (Smith), the goalkeeping coach. He has to go on the pitch and keep working with Darlow. We have to work with them and talk again. He’s being treated as normal. It doesn’t have to be a problem.
“He’s a young lad coming to a new country. I think he has a great future.”
Asked if Sels would start against Norwich, Benitez said: “I don’t know. You will see. I will decide.”
Benitez is relaxed about his players having a presence on social media sites like Twitter and Instagram.
But he is only concerned with football, and not followers.
“Every year we talk about referees, big decisions and about social media and advise how to manage it,” said Benitez. “It’s part of life now ... Snapchat, Instagram, on the phone. The best way sometimes to is forget about it.
“Some players have a name and an image, that’s fine.
“Sometimes it’s best to forget about social media and concentrate on your job. You don’t improve on the pitch the more followers you have.”
Benitez again talked about the need for unity on Tyneside ahead of the Norwich game.
Asked what his message to those supporters who trolled Sels with vile abuse, Benitez said: “I don’t have to give advice to anyone.
“I have my opinion without telling them what they have to do. If we want to be stronger we have to stay united.
“I don’t see any player changing his technical ability because someone is booing him or criticising him. Matt Sels is a really good professional.
“The majority of our fans know they have to support the team. As a manager I always support the players on the pitch
“The fans, even more than me the majority, really feel the club. They live here and are passionate about the club.
“They want the best for the club, to win every game and be in the Premier League. The fans realise that to support the team especially during the games is crucial.”