Much of their season has been characterised by a knack of grinding out results without playing particularly well but the performance over both legs of a 3-1 aggregate victory against the London side was all about style and class.
Manager Sir Alex Ferguson has been quick to point out that this season is very different to 1999 because of the injuries they have suffered but his players have recovered just in time for the run-in and returned with a new spark.
"I think we've hit our form," said Ferguson after Tuesday's 2-1 victory at Old Trafford. "I don't think there's any doubt about that. You've seen it in the second half at West Ham (a 4-2 win after being 2-0 down at half-time) and the (first leg) performance at Chelsea, plus the performance tonight."
The Scot has said the return of key players such as centre-back Rio Ferdinand has been like signing new players but with the added bonus that they already know how to play for the club.
Ferdinand, who started limping early in Tuesday's 2-1 win at old trafford but battled on, was just one of several key figures who were outstanding in a team whose cohesion is growing.
Mexico striker Javier Hernandez, goal-poacher in chief, has been a revelation and his knack of netting at key moments has kept top scorer Dimitar Berbatov on the bench.
ENERGETIC ROONEY
Wayne Rooney has gelled better with Hernandez than Berbatov and seems to be revelling in a deeper position behind the Mexican that is proving very effective.
"He (Rooney) is enjoying the position he's playing in at the moment because it has given him a lot of freedom to use his energy, in that position you do need energy," Ferguson told a news conference after Tuesday's victory.
In the first leg Rooney was given too much space and scored the only goal of the game, and while Chelsea changed their shape to try to restrict him in the return leg he still pulled the strings and used his eye for a long ball to devastating effect.
Similarly effective has been the evergreen Ryan Giggs, who was involved in all three of his team's goals in the tie, a feat made all the more remarkable by the fact he is now 37.
Giggs knows what it feels like to win the treble and that could be key as United seek success in the Champions League, Premier League and FA Cup.
"His experience and composure are vital," Ferguson said of the Welshman. "He's just a unique person and player.
"He's lucky, in the sense he's got a physique that doesn't carry any weight, he's got fantastic balance... he looks after himself. To play at 37 years of age there must be tremendous sacrifice to do that."
Ferguson was heading to Germany on Wednesday to find out who his team will face in the Champions League last four, although it is likely to be Schalke 04 who lead holders Inter Milan 5-2 from the first leg at the San Siro.
If United win the semi-final, a trip to Wembley for the final would beckon and they will have an early chance to get a feel for the turf this Saturday when they face lco
