Borussia Dortmund midfielder Gundogan will miss the Euro 2016 finals in the summer after dislocating a kneecap in training.
Ozil has taken to Twitter to send a heartfelt message to the 25-year-old.
Gundogan is one of the best players in the Bundesliga and is a key member of the Germany national football team.
The injury to the former FC Nurnberg midfielder will be a blow to Germany, and it also raises doubt on his future.
The 25-year-old has been linked with a move away from Dortmund in the summer transfer window.
Given the seriousness of the injury suffered by the German, City could decide not to pursue a deal for him in case he does not recover fully in time for the start of next season.