David Moyes insists it will take time to assert his influence on Manchester United and the Scot is braced for more difficult days like Sunday's derby humbling at Manchester City.
Moyes came in for more criticism after the 4-1 drubbing at the Etihad Stadium, making Wednesday's Capital One Cup clash with Liverpool even more important for United.
The former Everton boss has conceded he is yet to properly settle into life at Old Trafford, but is focused on success in the long run.
"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."
United are expect to recruit in the January transfer window and Moyes has set his sights on players who are ready to make an immediate impact on the first team.
"I don't think it's actually the squad, I think we've got numbers," he added. "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."
When asked if he was ready for the challenge of managing Manchester United, Moyes said: "I thought I was (prepared) but obviously when you come here then I realise maybe I wasn't.
"It is a club on its own. It is 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."
Information from the Press Association was used in this report.