Ferguson, who saw his side win the 17th trophy since he took over the reigns at Old Trafford, was delighted with Ronaldo's stunning display.

The £12.24m signing gave United the lead on the stroke of half-time when he headed home from eight yards out.

The goal proved to be crucial as any hope that Millwall went into the match with soon evaporated as United clicked into cruise control in the second period.

"Ronaldo was outstanding," said Ferguson. "We need to look after him in the right way because he is going to be an outstanding footballer."

"You have to respect your opponents at all times and never take them for granted," he added. "It took most of the first half to open them up.

United and England right-back Gary Neville was also keen to highlight the performance of United's Portuguese starlet.

"Ryan Giggs and Ruud van Nistelrooy produced some good moments for us, but Cristiano Ronaldo was particularly outstanding," he said.

"I think Ronaldo can be one of the top footballers in the world.

"To come with the price tag on his head and at his age, he has been outstanding for us this season."