Rafa Benitez can took charge of the North East club a couple of weeks ago with Newcastle desperately fighting to avoid relegation. The side have won just six league matches all season.
And Keegan has also indicated he wouldn’t have felt happy making that statement had the club kept Steve McClaren in charge.
Speaking to the Chronicle, Keegan said: “It’s a really good appointment. He will keep them up but it won’t be easy. They (Newcastle United) have got some home games that are winnable.
“I think Newcastle were going down without making the change, to be honest, with the greatest respect to Steve McClaren.
“I have looked at the fixtures, and they have got to win these home games. Anything they get away from home, like at Norwich and teams around them, will be a bonus.
“It looks to me like Norwich, Aston Villa and either Sunderland or Newcastle are going to go down.”