Japan striker Yuya Osako could miss Cologne's next Bundesliga game at the weekend against Wolfsburg due to a knee issue, the German club said on Tuesday.
Although the injury is not serious, it is unclear how long it will take Osako to make a complete recovery.
Osako hurt left knee ligaments in a collision with Stuttgart goalkeeper Przemyslaw Tyton after coming off the bench on Sunday, but he continued playing and scored in injury time to complete a 3-1 season-opening win.