Berbatov said: "It's a very tough situation, especially for a young player.
"It shows you how football can be a really cruel game at times because Kobbie Mainoo was playing, he reached the England national team, he was going up, up, and up. All of a sudden he is not being picked.
"Now the question is, does he stay positive, patient, and wait for his moment again? Or he needs to move to a different place to play regularly to get his confidence back and come back to United and start playing more regularly?
"I'd like to see him play because the talent is there to see, that decision-making, that calmness and arrogance which you need with the ball at your feet is there, even at his age. I like that. But at the moment, the manager doesn't see something he can use from the first minute of the game."