Cathro stayed on at United after Paul Simpson, Alessandro Schoenmaker and Steve Black all left the club, along with former head coach Steve McClaren .
Geordie coach Black showed his class on Friday night when Tweeting his best wishes to the fans for the rest of the season.
But speaking on why he retained Cathro and goalkeeper coach Simon Smith, Benitez said: “I had a very good reference about them.
“So obviously they will help us because we need to know all the details and that can make a big difference.
“I was talking with Ian already, and Simon was the same with the keepers and what we want to do.
“It is still early but I could see that they know everything and that will be very helpful for us.”
Benitez does have sympathy for McClaren and said on NUFC TV: “Steve is a friend. I know what it means to be fired from a team when you are working so hard.
“He was giving everything and trying his best.
“In football these things can happen, but I wish him all the best for the future.
“Hopefully we can win and do well and it will part of his job here.”
Meanwhile, Black’s words on Twitter resulted in plenty of well-wishers thanking him for his efforts.
Black said: “All the very best to Rafa and his team. Let’s hope they can bring the success this great club and the city deserves and needs.
“Black and white forever!”