James Morrison admitted the youngster did let things go to his head earlier this year.
Downing said: "I read something about what Mozza said and he was an immature boy who got carried away.
"The England thing would distract him because he'd go and play for the under-17s or 18s and the environment means you're mixing with Manchester United, Chelsea and Arsenal players, and he would come back a little bit excitable and we would try to calm it down.
"Sometimes there might be a little misdemeanour here or there where he hasn't trained properly or poor timekeeping, all minor things.
"But I've seen in the last six months, probably since his knee injury, that he's really knuckled down and I think something has hit home."
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