The 22-year-old, who joined the Bundesliga outfit from Twente last summer, has been used as a substitute in the last two matches and has scored only six goals in the league all season.
"The coach [Lucien Favre] has decided that way," De Jong told Express. "I hope, I can be part of the team again soon and help on the pitch.
"Of course you are disappointed when you are not playing. I need to show I want to play in training every day.
"There have been other strikers who did not have the perfect first year in Bundesliga. I scored important goals and I need to keep on working."
De Jong has made 21 appearances in the Bundesliga all season.