Scotland coach Craig Levein claimed that the 28-year-old has enjoyed a "dramatic improvement" in his fitness as he bids to return from ulerative colitis and is to link up with the squad purely to train ahead of an international friendly with Australia.
However, Phelan is keen to stress that Fletcher will be nursed along carefully as he battles the serious bowel condition that necessitated an enforced lay-off from the game last season.
"Darren joined in for four or five days last week," he told MUTV. "We decided that, if he felt well enough and felt good, we'd bring him into a training session.
"That's developed a little bit longer than what we actually thought. I don't know what the position is but if Scotland want to take him, it's probably just to be part of the squad and to introduce him back into that.
"But there's a long, long way yet for Darren Fletcher before we see him playing again."
Meanwhile, Phil Jones left the squad in Gothenburg to return home with a back spasm but could be available again in time for Saturday's Chevrolet Cup fixture with Hannover.
"We just sent him back," stated Phelan. "There's no point having a player out here if he can't train so we sent him back.
"He's had an examination and should be ready for Thursday or Friday at the end of this week."
The assistant manager also had words of encouragement for new signings Shinji Kagawa and Nick Powell