He joined Manchester City in June, but Ilkay Gundogan says a return to Borussia Dortmund in the future remains a possibility.
Ilkay Gundogan has made a swift impact at Manchester City, but says he cannot discount the possibility of rejoining Borussia Dortmund further down the line.
The Germany international, 25, completed a switch to City from Dortmund in June, agreeing terms on a four-year contract.
Following knee surgery that saw him miss Euro 2016, Gundogan had to wait until last week to make his City debut - a 4-0 rout of Borussia Monchengladbach in the Champions League.
A first goal followed in Saturday's 4-0 Premier League win over Bournemouth and Gundogan wants to prove himself away from Dortmund before considering any potential return to the Bundesliga.
"If it was the case in the next one or two years, I would probably not be happy about it," he told Sport Bild.
"Because it would probably mean that I have failed or not developed myself.
"If I'm 29 or 30, I do not know if [Dortmund would] still want me. Basically, I would not exclude the possibility, but now I have other big targets."