The Italian left Young at home when he named his 30-man squad for the World Cup in South Africa.
But he said: "What's changed with Ashley Young [since not going to the World Cup] is that now he is playing with a really important team.
"And he has improved a lot.
"Because the confidence, when you play in a really important team, improves a great deal.
"This is because of the quality of the players he is playing with.
"He can play as a second forward, behind Rooney.
"He played left-wing for a long time. He is technically good, fast, and has a good imagination. And he scores goals - he can shoot with his left and right."