The Red Devils last week splashed out an estimated £17m to bring in England winger Young from Aston Villa.
But Nani, who was left on the bench for May's Champions League final defeat despite earning United's players' player of the season award, believes he still has a future in England
"Of course I have to welcome everyone they sign," he said. "I think Manchester United is a fantastic club.
"When they bring in new players, they know if it is good for the team or not, and this signing has to help them. It is good for the team, we want more players to help us to win trophies.
"I've been at United when Cristiano Ronaldo was there. Cristiano was one of the best players in the world. At that moment I had no worries about him taking my place."