Watford forward Ashley Young completed his move to Aston Villa, for an fee of £8 million today.
Boothroyd said: “I think Ashley can kick on again because of his mental capabilities and the manager of the club he’s going to.
“I have a great deal of time and a great deal of respect for Martin O’Neill and I think anybody who goes to the club he is in charge of is very, very lucky.
“I think Ashley is worth the transfer fee. He might even be a bargain.
“He can cope with the expectations ahead. He is a very strong kid, very disciplined, the ultimate professional and he is going to have a very good career.”