Berahino, 21, came in for criticism earlier this week when he declared that he “hoped to move on to bigger things” during an interview with Sky Sports which his club hadn’t authorised.
West Brom are said to be furious with his comments, according to the likes of the Telegraph, and are now considering putting him up for sale in the summer after growing tired of his poor attitude, with Liverpool and Tottenham Hotspur named as two potential suitors.
The Mirror have also reported that his teammates have since been blanking him at the training ground, but Fletcher has refuted those claims, insisting that the striker remains a popular figure in the dressing room.
“I think that’s something he’ll learn from,” he said. “We’ve all been there and done stuff when we’re young that we later realise is going to be national news.
“I must admit, I’ve come here and been surprised at how nice he’s been – how friendly, how welcoming and how well he trains.
“You can get a certain impression of someone from the outside and it’s not been the case at all.
“He’s been a pleasure to work with these few days. He’s a kid still learning his trade, and obviously he’ll learn from the mistake he made the other day, and it’ll stand him in good stead for the future.
“I know he’s fully behind West Brom. In the dressing room he’s part of the team.
“A few of the lads have made him aware of his mistake, but it was all in good humour. He realised that and he’s going to be an important player for us this season.”
Fletcher, meanwhile, has revealed that confided in former boss Sir Alex Ferguson before making his last-minute move from Manchester United at the transfer deadline.
Having been on the books at Old Trafford since the age of 11, the Scotland international admitted that it was tough to leave the club behind, but is now looking forward to a new challenge at the Hawthorns.
"I spoke to him about the options I had and my feelings before I came here and he gave me fantastic advice," he said.
"He only wants the best for me and is someone I can lean on for advice at any time.
"He has never failed me yet and has always been spot on and he gave me some good advice."