BBC Sport looks at how Manchester United prevented Chelsea from claiming a third successive Premiership title.
Sir Alex Ferguson's ninth league success at Old Trafford came without his side kicking a ball as Chelsea drew 1-1 at Arsenal on Sunday.
Chelsea finished eight points clear of United last season and 18 the season before - but following the Blues' draw, Ferguson's team have an unassailable seven-point lead with two games to go.
But how have United managed to overtake Jose Mourinho's team to land their first title since 2003?
SOLID AT THE BACK
Chelsea are a brilliantly organised team who remain extremely difficult to break down.
Even though they have lost their Premiership title they have kept more clean sheets than the champions, with 21 to United's 15.
However, unlike in the previous two seasons under Mourinho they have found themselves over-stretched defensively - particularly in the centre.
William Gallas and Robert Huth left the club last summer while John Terry, Ricardo Carvalho and Khalid Bouhlarouz have all missed games through injury.
Influential skipper Terry missed a crucial eight weeks of the season during December and January. And it is no coincidence that Chelsea conceded twice in each of the first four games Terry missed over the Christmas period.
Chelsea's defence has suffered injury problems at key times
The lack of numbers in the centre of defence was an issue that Mourinho wanted to address in the January transfer window but he was not given the funds to do so.
The knock-on effect was that Michael Essien often found himself drafted into defence and his all-action displays were sorely missed in the heart of the Chelsea midfield.
And Petr Cech, widely regarded as the world's best goalkeeper, missed several months with a fractured skull - further weakening Chelsea's defensive unit. Ashley Cole has also suffered from injury problems.
Manchester United manager Sir Alex Ferguson had struggled to fill the goalkeeping void left by Peter Schmeichel following his departure from the club in 1999.
A succession of keepers have been and gone but in Edwin van der Sar, Ferguson has finally found a suitable replacement.
Serbia defender Nemanja Vidic has also enjoyed a fine season in the centre of defence, with his no-nonsense defensive style complementing Rio Ferdinand's more cultured approach.
Patrice Evra has matured at left-back while Gabriel Heinze has proved versatile and effective when required.
United also suffered from injuries - but Ferguson's team already had a solid lead at the top of the Premiership by the time Gary Neville, Vidic and Ferdinand were sidelined in the latter stages of the season.
United's defence has often been regarded as error prone over recent seasons but it has had a more solid look this time around - and been excellently protected by summer signing Michael Carrick.
And although United have kept fewer clean sheets than the Londoners, they have only conceded one goal or more in a game five times compared to nine by the Blues.
THE ENGINE ROOM
One crucial difference between this season and last has been the return of Paul Scholes.
Scholes missed five months of the last campaign with an eye problem and his presence has restored craft and maturity to the United midfield.
Carrick and Scholes have been superb in the centre of midfield
His range and accuracy of passing has allowed United's myriad attacking talents to flourish and he has formed a superb combination alongside Carrick, whose form has gone a long way to silencing those who questioned the value of his £18.6m transfer fee.
One of Chelsea's big summer signings was Michael Ballack who joined on a free transfer from Bayern Munich.
The German has had a disappointing season, not gelling with Frank Lampard in the middle of the park and looking a shadow of the player who was so dynamic for Germany at last year's World Cup.
Nigerian Jon Obi Mikel has been impressive since Christmas and has started to justify the hype but injuries elsewhere have meant that all-too-often Essien has been played in defence.
WORKING OUT WIDE
Mourinho's first two seasons at Stamford Bridge saw him favour the use of three in midfield, with two wide players and a solitary striker in front of them.
The Chelsea boss had an impressive pool of wide players in Joe Cole, Arjen Robben, Damien Duff and, for his second season at the helm, Shaun Wright-Phillips.
Ronaldo has been brilliant for Man Utd this season
But Cole, so impressive for Chelsea in recent years, has missed all but a handful of games this season, while Robben has also spent large spells on the sidelines.
With Duff sold to Newcastle last summer and Wright-Phillips often overlooked, Chelsea have not been as effective down the flanks.
United boss Ferguson also understands the importance of width and in the evergreen Ryan Giggs has a veteran winger who is both consistent and potent.
But the revelation has been Cristiano Ronaldo.
His Premiership future seemed in doubt when he was accused of playing a role in Wayne Rooney's dismissal against Portugal at the World Cup last summer.
But the Portuguese youngster has been the Premiership's best player this season.
The 22-year-old has learnt to refine his vast array of skills. Instead of constantly overplaying he has used his gifts to hurt the opposition - as his return of 17 Premiership goals testifies.
FINDING THE NET
Didier Drogba's third season in English football has been an unqualified success.
The Ivorian is the Premiership's top scorer with 19 goals and his combination of physical power and finishing ability has proved too much for many defences.
Unfortunately for Chelsea their £30m summer signing last summer Andriy Shevchenko has endured a difficult first season in England.
The Ukraine star's return of four Premiership goals from 22 starts and eight substitute appearances tells its own story.
His inclusion in the side alongside Drogba required a change of formation, while rumours that his signing was instigated by owner Roman Abramovich cannot have helped.
Drogba (left) has been excellent but Shevchenko has struggled
United sold Ruud van Nistelrooy to Real Madrid last summer.
The Dutch striker was prolific for United, with 95 Premiership goals in 137 starts - but with his presence came a relatively fixed style of play.
United's forward line this season - with the likes of Louis Saha, Wayne Rooney, Henrik Larsson, Giggs and Ronaldo - has been fluid and inventive and have not relied on van Nistelrooy to apply the finishing touch.
HARMONY AND HEARSAY
The good times have rolled down the Kings Road in the past two seasons as Mourinho, financed by the millions of new owner Abramovich, delivered back-to-back Premierships to wrestle the balance of power from Manchester United and Arsenal.
This season, however, the relationship between Mourinho and Abramovich has been the subject of constant speculation.
Their relationship is reported to have soured, leading to repeated suggestions that the Portuguese will not be in charge of the club next season.
Relations have been frosty between Abramovich (pictured) and Mourinho
Abramovich is said to have favoured a more attacking style of play and wants to win the Champions League above all else.
Mourinho, on the other, was extremely candid in January, explaining that although he wanted to sign a defender, the board would not provide the necessary funds.
Chief executive Peter Kenyon made it clear in April that Mourinho would remain at the club - but the months of rumours may have unsettled a group of players trying to close the gap on United.
Recent seasons have seen unrest and uncertainty at Old Trafford - a situation that arose prior to, and following, the takeover of the club by Malcolm Glazer.
The American borrowed heavily to finance the purchase and many supporters feared it would necessitate radical and unwanted changes to their club.
Their worst fears have not materialised, while the Glazer family, with Malcolm's five sons and one daughter occupying six of United's seven boardroom seats, have maintained a low-key presence.
Ferguson does not seem to have been hamstrung in the transfer market and without the constant distraction from off-the-field issues the manager has been able to ensure everyone has been focused on what matters most - winning games.
Both Chelsea and Manchester United have enjoyed lengthy periods of excellent form.
Crucially, though, it was United who made the best start, moving to the top of the Premiership and subjecting Mourinho's Chelsea to the role of pursuers for the first time.
United lost just one of their first 17 fixtures, drawing two and winning 14.
During the same period Chelsea lost two and drew three, winning 12 to give United a five-point lead.
Chelsea won nine straight games starting on 31 January - their longest winning streak of the season. United responded with seven consecutive victories of their own before losing to Portsmouth.
It seemed as though United might crack under the pressure of Chelsea's brilliant run but Mourinho's team lost crucial momentum with draws against Newcastle and Bolton.
In the end it seems Chelsea left themselves just too much ground to make up on their rivals.
It was a frustrating end of the season for Mourinho
Chelsea have won 29 games in each of their title seasons.
Last year they drew four and lost five on their way to the title, the season before drew eight and lost just once. This season Chelsea have drawn nine and lost three - with a maximum of 26 wins possible.
Chelsea won the title in 2005 with 95 points and the year after with 91. This year they can still reach 87 points.
It is not that Mourinho's team have suffered a dramatic lowering of standards, more that for the first time they have been seriously challenged.
United finished with 77 points in 2005 and 83 in 2006. This year they have played more consistently than in recent years and with a team that has a superb blend of experience and youth, United can finish the season with 94 points.
The coming together of the two clubs owes more to United's improvement than Chelsea's decline - and it has made for a brilliant title race.