Benitez – who took over from sacked head coach Steve McClaren last week – is preparing the team for Sunday’s Tyne-Wear derby against Sunderland.
And Marcelino – who had an injury-hit spell at St James’s Park during Sir Bobby Robson’s memorable tenure – believes Benitez can keep the second-bottom club in the Premier League.
Now a TV pundit, Marcelino, signed from Real Mallorca in 1999, feels Newcastle couldn’t have signed a better manager.
The 44-year-old was at the King Power Stadium on Monday night for Benitez’s first game in charge.
While United were beaten 1-0 by league leaders Leicester City, Marcelino is hopeful the club can stay up.
“Rafa has a very big reputation,” said Marcelino.
“He’s been at top clubs and won trophies at top clubs.
“There are not many managers of his level who will be keen on working for a club in a relegation position. You have to be realistic about that.
“I think Newcastle is a top club, but they are struggling at this moment and not every manager would have the courage to take charge of a team that is fighting relegation.
“He’s shown with this decision that he feel capable of bringing Newcastle safety.
“If he believes that, I have to believe in him.
“It makes no sense that someone like him gets himself into something that will cause him problems.
“From that point of view, I think Newcastle has signed the best manager possible if they wanted to sack the existing one.”
Champions League-winner Benitez – who started the season as Real Madrid manager – is more used to coaching teams challenging for trophies.
And Marcelino feels the former Liverpool and Chelsea manager wouldn’t have taken the job on if he had any doubts about his ability to keep the club up.
“Managers don’t want to damage their reputation with relegation,” said Marcelino. “He’s coming from managing Real Madrid.
“If he comes to Newcastle, it’s because he believes he can save the season and do a very good job here in the Premier League. That tells me a lot about him.
“I believe that with him Newcastle will be safe at the end of the season.”