Although he inherited a squad that won the Premier League title by 11 points last season, many felt the manner of that success masked some clear deficiencies.
They were underlined by Sunday's 4-1 hammering at Manchester City, which puts a whole new perspective on tonight's Capital One Cup tie with Liverpool, featuring the return of Luis Suarez.
But Moyes feels the pain may not be over just yet.
"It was always going to be tough following such a great manager with a great team and I think people with real football knowledge will know there are probably some changes to be made," he said.
"It is not going to be made in one fell swoop. It is going to be done in time.
"That is why the Manchester United board realised the job that needed to be done was a long-term one.
"There was always going to be days like this and there might well be more days like this."
That Moyes dispatched coaches Nicky Butt and Phil Neville to Spain at the weekend to run the rule over Espanyol defender Hector Moreno and Athletic Bilbao midfielder Ander Herrera underlined the changes that need to be made.
"I don't think it's actually the squad, I think we've got numbers," said Moyes.
"Maybe we've got work to do to bring in players not for the squad but to go right into the team.
"That will happen. But going back to that transfer window, we always said it was going to be a tough one and it was going to take a little bit more time."
It was said to Moyes at various stages of the summer that nothing could quite prepare him for life at United.
That has been brought into sharp focus by the reaction to Sunday's defeat, that has swung sharply between understanding and sympathy to outright hostility.
"I thought I was (prepared) but obviously when you come here then I realise maybe it wasn't," said Moyes.
"It is a club on its own. It is a fantastic place to work with great players.
"But we have to do well enough to make sure people on the outside think the work we are doing is the right stuff."