The 19-year-old, son of former Red Devils’ midfielder Darren, was a shock pick for the Tartan Army after only 45 minutes of international football, following an emergency call up to replace the injured Billy Gilmour.
But Norwich City captain McLean has become something of a mentor for his fellow midfielder.
“I knew Scott (McTominay) from United he has helped me a lot. Kenny McLean has unbelievable with me,” said Fletcher, speaking to Scotland’s official Youtube channel. “Top guy and honestly one of the best players I have ever trained with. He is so good. To be honest all of them are brilliant and a great team to be around.
“It’s been a crazy period but I am loving every minute of it. After the (Curacao) friendly I found out Billy had got injured and I was gutted for him but the manager came up to me and said it might not be the last time I see you on this trip.
"The next morning I got a call at 8am, ‘Do I want to go to the World Cup?’ I was speechless but said, ‘Yes’. I rushed to the hotel to get on the bus to go to the airport. I had nothing with me. No boots, they had to be sent over.
“(Dad) didn’t go to a Euros or a World Cup his whole career and I have managed it after 45 minutes of senior football. But he is buzzing for me. He’ll be out for every game. Everyone wants to create history. I want to enjoy the experience and hopefully get on the pitch and play in a World Cup.
“It is a good level. A tough challenge and the heat is hard to train in, but I feel comfortable and ready to go. I felt if I could make an impression and I could be around the first team but to get to the World Cup was something I never dreamed of.”
McLean played with Fletcher's dad at the start of his own senior international career and is convinced the teenager has a huge future in the game.
“I can't speak highly enough of him,” said the City captain. “I said to the lads after his first session, 'I can see something special in him' so I was glad he got on (against Curacao) after the week he had.
"In my first couple of squads I played with his dad. And, for me, in my first session he also stood out a mile.
"Fortunately for Scotland, his son is pretty similar. There is a lot of potential there. It's about using him in the right way.
"Hopefully he does that back at his club and then when he comes away here and when he gets the opportunity, he makes the impact he has already.”
Scotland are based in North Carolina for the tournament, and kick-off their World Cup campaign in the early hours of Sunday (UK time) against Haiti.