Fletcher, Levein's captain when he was Scotland manager, made his first appearance in a Manchester United shirt for 10 months on Monday, playing 67 minutes against Fulham under-21s as he steps up his return to full fitness. The midfielder missed most of last season after undergoing surgery for the bowel condition ulcerative colitis.
Levein elected not to reveal details of the extent of Fletcher's suffering but hopes the 29-year-old has taken the first step back on the road to a first team return and then, eventually, international football. Fletcher last played for Scotland in the friendly win over Luxembourg in November last year, and has yet to feature under Gordon Strachan.
"It was excellent to see him play the other night," Levein said. "He is a top, top bloke. He will never talk about it or let you know exactly what he has been through. But if he ever writes the book it's worth reading, I can tell you. I have been in constant contact with him. He is an absolute diamond of a bloke and has shown remarkable fortitude after what has happened to him and interrupted his life for as long as it has."
For Levein, it would be a pleasure to see Fletcher back in a Scotland jersey. "It would be brilliant, it really would be," he added. "He will be looking at playing some more games, I think it was only about 70 minutes he played the other day.
"He will be looking at getting back into that Manchester United first team. If he does that it will be significant as an achievement. After that, I'm sure any player of his quality would be welcome back in the international squad as soon as he is ready. It's not my place to talk about what he has been through. But I can assure you it hasn't been pleasant at all."
Levein, of course, will not be around whenever Fletcher does return to the international fold. Tuesday will mark the one-year anniversary of his departure from the Scotland job, and the subsequent period for reflection he has been afforded has left him philosophical about the travails he endured.
Under Strachan there has been a marked improvement in Scotland's fortunes in recent months but there is no bitterness on Levein's part about his successor seemingly thriving where he fell short.
"Do I regret taking the Scotland job? No, How could I? I had some brilliant times," the former manager said. "It was just the level of expectation, that's all it is. Things don't go your way and I can think of three or four occasions where one thing going for or against us made a big difference.
"There is nobody happier than me that things are turning round. The game over in Croatia was a huge turning point. That allows the removal of the shackles. People are saying, 'wait a minute, if we go to Croatia and win then we can't be that bad a side'. Gordon has done a brilliant job, I've an awful lot of time for him. But he now has a group of players growing in confidence. And with that the media and punters are more confident as well. You get a little bit of momentum going which I didn't manage to get. I didn't get to that point. I take pride in the fact I was the manager and I'm still in contact with some of the boys. They were trying really hard and not getting any reward for it. Now they are getting reward."
Levein hopes to return to management soon but ruled out another international post. "I've had a couple of offers and people making a note of interest in me. I thought I had a good chance of getting one job in particular and I've been in for another two or three on top of that.
"I've had to take a step back and when I go back it will be a club job. A guy phoned me about an international one, but that's not for me. I have too much energy for the sporadic stuff."