Manchester United manager David Moyes has said he's still short of players ready to go straight into the English champions' first-team and warned fans to prepare for more days like last weekend's derby defeat.
United were thrashed 4-1 by Manchester City, a result immediately billed as a demolition derby, on Sunday.
Moyes, speaking ahead of Wednesday's League Cup tie against arch-rivals Liverpool, said he was under no illusions about the scale of the task confronting him in succeeding retired United manager Alex Ferguson, who bowed out with the team winning the Premier League by 11 points last season.
"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," Moyes said in comments reported by Britain's national press on Wednesday.
"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," the Scot added.
Moyes's delayed arrival from Everton meant the only major signing United made during the last transfer window was Belgium midfielder Marouane Fellaini from his old club.
United failed in their attempts to bring Spain Under-21 captain Thiago Alcantara and midfielders Cesc Fabregas, Ander Herrera and Daniele de Rossi to Old Trafford.
Meanwhile Everton's Leighton Baines remained at Goodison Park while fellow left-back Fabio Coentrao could not be enticed away from Real Madrid.
"I don't think it's actually the squad, I think we've got numbers," said Moyes as he prepared to face a Liverpool side set to be buoyed by the return from suspension of striker Luis Suarez.
"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."
Moyes accepted that for all his long experience of football, which he hoped had prepared him for the daunting task of succeeding Ferguson, nothing could compare to the job of actually being United manager.
"I thought I was (prepared) but obviously when you come here then I realise maybe I 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," he added.