Sir Alex Ferguson has hailed Sunderland's recent win at Chelsea as "the perfect performance".
Ferguson sends table-topping Manchester United into battle against the Black Cats at Old Trafford on Boxing Day already acutely aware of the challenge posed by Steve Bruce's men, who swept to a 3-0 victory over Chelsea at Stamford Bridge five weeks ago.
"In all the time I have been at Manchester United, I could probably point to six perfect performances. Steve will look at that in the same way. It was one of the stand-out performances of the season," said Ferguson.
"They were absolutely brilliant and could have won by six or seven. It is a reminder that we are dealing with a team that has that kind of ability and drive at the moment. We are in for a particularly hard game."
It did not escape Ferguson's attention that one of his own helped do the damage that day. Having loaned Danny Welbeck to Sunderland for the campaign, Ferguson has been encouraged at how the 20-year-old has eased himself into the first-team picture.
Taking advantage of the knee injury that has ruled one-time Old Trafford colleague Frazier Campbell out for six months, Welbeck has responded positively to the challenge provided by fellow forwards Darren Bent and Asamoah Gyan.
He has scored four times since breaking his drought at Stamford Bridge and, although he cannot face his parent club on Sunday, Ferguson confirmed he believes Welbeck is now one of Sunderland's main men.
"In his spell around the first team in the last couple of years, Danny never played more than four games in a row. It was imperative that he went out on loan and played regular football," observed the Scot.
In addition, part of the aim was to get Welbeck used to his own body, which had been growing at an alarming rate.
"In the last couple of years he grew so big, so quickly, Danny was weak in some parts of his legs, which created a lot of problems for the boy," added Ferguson. "But you look at him now and see the growth. He has filled out and is very powerful. He is handling the physical part quite easily and has been one of Sunderland's best players."