The 25-year-old received the support of his manager Thorsten Fink, who agreed to a request from the player for his condition to be investigated.

"At the end of the pre-season, I found it harder and harder to get up," Aogo told Bild.

"Body and mind are interrelated. I thought that it was just a phase but the point came when I could no longer help the team.

"I was depressed and mentally I felt that I was no longer myself. Therefore, I asked the coach if I could get it checked thoroughly."

Aogo spent over a week receiving treatment and said he is relieved to be back to his normal self again.

"After 10 days (of care) the motivation and momentum came back. This was not an easy time but I feel really good again," he said.