The 29-year-old, who has been plagued by the illness for almost two years, made his return to action in a reserve match on Monday evening.
"It is great to get Darren back," The Mirror quotes Moyes as saying. "It was the first time he pulled on a jersey in a competitive reserve league game [since the operation] and we're really pleased.
"We will bring him along, his training is coming along well, but we don't want to do anything that might give him a setback.
"It is a sort of steady, slow grind for him just now, but we are pleased and hope to involve him in the upcoming reserve games in the weeks to come, if he continues to do as well as he is doing now."
Fletcher underwent surgery on his ulcerative colitis condition in January.