The £71m signing from Brentford is waiting to make his first appearance for United in preseason.
Mbeumo's former Troyes teammate Franck Momo told The Sun: “Believe me, Bryan will have a big impact in that dressing room.
“He hates to lose so much it's crazy. In the beginning he’ll be shy, but once the season goes on, his personality and professionalism will shine. His teammates will follow his lead.”
Momo also recalled: “He was with the 1999 age group, I was two years older but one thing was certain he wasn’t the best player on paper.
“I remember the first time when he was promoted to come and play with us in the reserves team and I asked the coach why Bryan and not the others. I got a simple answer.
“He told me, ‘Bryan’s the most efficient. He knows his strengths and works on them every day.’
“Looking back now, it’s like he knew what he was doing.
“He’s made it to Man United now but at the time, going from Ligue 2 to the Championship, it didn’t make sense to most people.
“Like think about it, he could have gone and still be in France but he just decided, this is where I want to be.”