Midfielder De Jong, who heads to Barcelona next season in a 86-million euro deal, had been doubtful due to an adductor injury but his coach confirmed his availability for the last-16 first leg on Wednesday.
With an impending move to La Liga, Ten Hag said it was natural that De Jong would want to impress against Real.
“But I think that is true for all our players. The opponent is an enormous challenge and we are all looking forward to it,” the coach told a news conference.
Ten Hag said Real would be favourites with Ajax still short of experience at the highest level after finishing second in the group phase behind Bayern Munich.
“With us, our inconsistency has to be removed. We underperformed against Heracles and Feyenoord in the league,” he said of recent domestic defeats that left Ajax off the pace in the Dutch title race.
“Nobody wanted what has happened to us in recent weeks but in other games we were good again. No team is able to keep up a rising line," Ten Haag said.
“We must come out stronger here but playing against Real is a big motivation. It is a match for a place in the quarter-final of the Champions League and we have to enjoy the experience.”
Ten Hag said he was considering fielding Brazilian winger David Neres after his strong performance against Bayern in October despite a lack of game time.
“It is an option to start with him and Dusan Tadic in attack, but Kasper Dolberg and Klaas-Jan Huntelaar are also great strikers who give us options,” the coach said.
(Reporting by Mark Gleeson; Editing by Ed Osmond)
