Carlos Queiroz has left his job as Manchester United assistant manager to take up the coaching reigns with Portugal.
Queiroz has signed a four-year deal with the Portuguese FA and said: "I'm very proud and honoured to go back to serve my country.
"This has been a special period in my life both personally and professionally.
"To Sir Alex, I thank him for his faith in me and his knowledge, spirit and desire from which I will take strength and have confidence in my new role."
Although disappointed to see Queiroz leave the club, Ferguson was full of praise for his former assistant.
"Carlos is one of the best coaches in world football," Ferguson told United's official website. "His attention to detail, ability to innovate and will to win have been a key factor to the team's recent successes.
"He has played an important role in building and blending the exceptional squad of players at the club."