The 29-year-old has been put on a strict diet and had several operations since being diagnosed with ulcerative colitis in 2011.
He played 13 games since then, but a definitive comeback has still eluded him.
"I'm staying away from the training ground right now because it's difficult being there when you are not actually training," said Fletcher.
"I've spoken to the manager, he seems great and we have discussed the plan going forward.
"I just can't wait to go back when I'm ready to get back training, not just plodding around, no use to anyone."
The Scotland midfielder also admitted that he has been doing a little work in the gym but has not resumed any training yet.