Moyes vindicated by Rooney's form
Rooney found the net in England's World Cup wins over Montenegro and Poland over the past week to guide Roy Hodgson's men into the World Cup finals.
It follows on from his outstanding efforts for United with Rooney, 28 on October 28, having scored five times in his last six games.
"I saw him like this on the first day of pre-season yet I had to keep telling everyone that was the case because the media thought it was different," said Moyes.
"I saw him in great form. He was in great fettle. His training was fantastic from day one.
"But people kept saying different things and I found it difficult to prove it different.
"You can see by his form and the goals he is scoring that what I was saying was right."
As Moyes acknowledged, Rooney is now approaching a point in his career when he is expected to handle more responsibility.
And he is pleased to note the former Everton star is doing exactly that.
"He is at an age where he would be one of the main players," said Moyes.
"He is certainly a main player for Manchester United and he is one of the main players for England.
"That is what we expected.
"He takes the responsibility, scores the goals when it is required. He has done that from a young age.
"But the age he is at now he has that maturity which shows in how he plays, the condition he is in and the way he is playing for both club and country."
Rooney is virtually certain to start against Southampton at Old Trafford on Saturday.
The big question is whether Adnan Januzaj will too.
It was the 18-year-old's two goals that turned potential defeat at Sunderland into victory on United's last outing a fortnight ago.
Yet, as Moyes pointed out, Januzaj cannot expect to be involved every week.
"I don't think anybody plays every week for Manchester United," he said.
"We have enough players to rotate the squad.
"Adnan is 18, does anyone expect him to play every week? Is he good enough? The answer is yes."
The only player who has started every game for United this season is goalkeeper David de Gea.
Amazingly, De Gea is not regarded as one of Spain's top three keepers despite earning selection for last term's Premier League team of the year.
However, Moyes has no doubt the former Atletico Madrid man will go on to become one of the world's very best.
"David had to come in and prove himself at Manchester United," said Moyes.
"Sir Alex bought him young and played him, at times when it was difficult because goalkeeper and centre-half are probably the two hardest positions to put out on the pitch for young players.
"Manchester United doing that over the last couple of years has shown what you can get.
"He is a top goalkeeper. He will go on in time to be one of the best there is. I have no doubts about that."
Victory over Southampton will shove United further up the Premier League table, although with three defeats already, Moyes' men have a bit of ground to make up.
However, Chelsea and Manchester City have also endured stuttering starts under new management and Moyes anticipates it will be later in the year before the picture starts to become clearer.
"It is a long season," said the Scot.
"Come the end of November we are getting much closer to the end of the year and we may well see things a bit clearer."