Fernando Santos does not understand why Manchester United let Nani leave but believes Portugal are reaping the benefits.
The winger has scored five goals in 14 games since rejoining his former club Sporting Lisbon on a season-long loan in the summer.
He had only started 14 Premier League games in his previous two seasons at Old Trafford and while Santos is glad Nani is featuring regularly again, he was bemused by Louis van Gaal's decision to allow the 28-year-old to leave.
The Portugal manager said in a news conference ahead of the friendly against Portugal: "It was very important Nani is playing in Portugal because he is playing regularly. It is good for us because that way he improves his form.
"Regarding why he went, you have to ask the Man United manager because I don't know why."
Nani is set to feature at Old Trafford again on Tuesday in a match which pits Cristiano Ronaldo against Lionel Messi.
The Real Madrid and Barcelona stars are also likely to go head to head for the Ballon d'Or award and Santos hopes his captain wins.
He said: "I voted for Cristiano because I think during the season he was the best player in the world. We all know Messi is a good player and in my opinion they are two geniuses playing football."