City, through to the last four of the Champions League for the first time, host Real in the first leg on April 26, and Benitez suggested their players might try to save their legs for their big European night, giving Newcastle an edge.
"In the back of your head you are thinking about a semi-final or a final and if you are going to get an injury," the Spaniard told reporters on Monday.
"They are professionals and they will try to win but in the back of their mind they won't want to miss a game through injury. I think they have an eye on the Champions League and hopefully we can take advantage."
However, City also need points to make sure they finish in the top four and guarantee a Champions League spot, with Arsenal level on points with them in fourth and fifth-placed Manchester United four points behind with five games left.
Benitez confirmed he would still be without injured captain Fabricio Coloccini, who has not played since February, while defender Darryl Janmaat, who missed the Swansea game with groin and hand injuries, has also not yet recovered.
Newcastle are three points from the safety zone and two behind north-east rivals Sunderland but with a gamne in hand over fourth-bottom Norwich City.
(Reporting by Simon Jennings in Bengaluru; Editing by Ken Ferris)
