Moyes watched Ronaldo's awesome performance for Portugal in their World Cup play-off victory over Sweden in Stockholm on Tuesday on TV.
Like everyone else who witnessed the winger's hat-trick, the United boss was spellbound by the talent Ronaldo displayed so regularly during his six seasons with the Red Devils.
Indeed, there was intense speculation during the close season Ronaldo was intent on heading back to his old club, with United eager to make a marquee signing to herald the arrival of Moyes as Sir Alex Ferguson's successor.
It did not happen. And now he has signed a five-year contract with Real Madrid, and declared his intention to remain at the Bernabeu for the remainder of his career, it seems highly unlikely it ever will.
However, maybe clinging to the most slenderest of hopes, Moyes is not giving up completely.
"Everyone at Manchester United would tell you he is the best in the business anyway," Moyes told MUTV.
"I have not been fortunate enough to work with him but there is still hope some day it might be possible."
With FIFA extending the voting period for the coveted Ballon d'Or prize, it seems certain Ronaldo will claim a prize he won for the first time as a United player in the 2008 Champions League campaign, when he scored an incredible 42 goals.
Former team-mate Anderson is in no doubts.
"When you have Ronaldo it makes it easy," said the Brazilian.
"He scores all the time. He scored three goals on Tuesday. He is an amazing player, for me the best player in the world."