Sankoh, 17, damaged ligaments in his left knee capsule in the first league match of the season 10 days ago. The forward underwent surgery last week which revealed that he may have to go under the knife again.

Stuttgart said doctors expect him to be sidelined for nine to 12 months.

“The doctors who treated him have assured us that the operation went well and that all of the structures will recover in the right way,” sports director Sven Mislintat said.

“That is a first important step for Mo and at the same time the beginning of a long road to recovery and back to the pitch. Mo will get all the support he needs from us and we are convinced that he has it in him to overcome this significant challenge.”

Stuttgart are also without Austrian forward Sasa Kalajdzic who injured his shoulder last week and is not expected to return this year.