Simon Grayson had no complaints about Alan Browne’s 27th-minute dismissal for an ugly challenge on ex-Sunderland midfielder Jack Colback.
Aleksandar Mitrovic had already headed the home side into the lead when Browne saw red, and with Mohamed Diame having doubled the advantage before the break, Matt Ritchie’s penalty and a delightful second from the Serbia international made the game safe within 10 minutes of the restart and set the stage for Diame and substitute Ayoze Perez to strike at the death.
Newcastle boss Benitez was refusing to dream of cup glory s he turned his attention back to the business of winning promotion.
Benitez said: “I have to concentrate just on Preston on Saturday, wait and see what happens in the draw and after, maybe I can answer those questions.”
The Magpies made seven changes, two fewer than the visitors, but they romped to victory.
Benitez, who was awaiting news of Colback’s condition after he was taken to hospital for an assessment, was delighted with his side’s display, but will take nothing for granted at the weekend.
He said: “They will try to amend the situation, they will try to change things, we will be playing away, so it will be totally different.
“It’s another competition, so we have to enjoy it. Normally I say one or two days and after, concentrate on the next game. It will be tough, for sure.”
On the changes, he added: “We have three or four players who have not been playing too many games. They come in and they play at this level, it can only be positive for the team and the future.
“I’m really pleased to see Mitrovic, Diame, (Christian) Atsu, or even (DeAndre) Yedlin. There were a lot of positives.”