The Cote d'Ivoire international joined the Bundesliga outfit from Ajax ahead of the current campaign, but was promptly sidelined following the discovery of a malignant tumour.

Since then, he has been undergoing treatment, with hopes he may yet be able to feature this campaign for Dortmund, as Edin Terzic's side hunt for domestic and European silverware.

Haller hopes to have the green light to return to action in the near future, stating he has ideas in his head - but admits it is all dependent on how his illness takes its course.

"I'm lucky enough to feel well," he said. "I am physically able to work, I feel fine from both a mental and a physical point of view, which is of course helpful to fight this disease.

"I have a timescale in mind. If I'm lucky enough not to need surgery, things can go very quickly. Checks are made three weeks after the final phase.

"If I don't need an operation, with the way I train, I'd like to think that I will be in good condition at the end of those three weeks.

"One of the first things I told myself was: 'OK, it's happened to me. I am going to do everything to be good mentally and physically'.

"I was a spoiled child; I never had any worries. This is the first big ordeal I had to face.

"Some people start their lives like that. I was lucky that it came later in my life, so I can’t complain. It's a challenge, a huge challenge, and the fact that you were able to overcome it means that you’re a warrior."