The German coach has lamented his club's inability to off-load their Danish defender who has returned to the Bundesliga outfit after a season on loan at Roma
The German tactician has revealed that the club and player had tried to part ways this summer, however, a lack of interest in the defender has meant that he will likely stay with the Bundesliga club for the upcoming season.
"The club and the player wanted to go their separate ways, however, the market has not made this possible. Nothing ever happened," Magath told a press conference.
With a number of central defenders already on the club's books, including the likes of Naldo, Marco Russ, Emanuel Pogatetz and Sortirios Kyrgiakos, Kjaer faces stiff competition for a starting berth.
Magath believes that the highly-skilled Denmark international will just have to make the best of it by working hard.
"Kjaer will just have to adapt," he said. "Simon is a good player with great skill. If he works hard, everything will turn out well."
Kjaer fell out of favour with Magath in the summer of 2011, prompting a loan move to Serie A with Roma.