Roman Abramovich bought Chelsea in the summer of 2003 and instantly reshaped English football. Within a month of the takeover he had spent £100 million on transfers, and although Claudio Ranieri did not win anything in the first year it wasn't long before Chelsea became one of the defining clubs of English football in the 21st century.
Here, we take a look at the three best individual seasons since Abramovich took ownership of the club.
Jose Mourinho – 2004/05
What they achieved
The first league title under Abramovich was arguably the most emphatic, and certainly the most important in laying the foundations for the project. Many feared the new owner would quickly get bored with his new toy; tasting major silverware so soon after the purchase might have been an important factor in Chelsea's long-term stability.
But putting Chelsea's future to one side, Mourinho winning the title in his first year in England was a game-changer for the Premier League. He ushered in an era of celebrity manager, made psychological warfare mainstream, and began an era of defensively-minded football in England.
Chelsea won the League Cup in February and the Premier League title in May, setting numerous records in the process, including fewest goals conceded in a season (15) and most wins in a season (29).
How they did it
Although often remembered as a purely defensive side, Mourinho didn't park the bus. His team's exceptional defensive record came from their ultra-compression between the lines, but that doesn't mean they sat deep. On the contrary, they were fearless in their approach, suffocating opponents in a hard-tackling midblock – before releasing their forwards on the counter-attack.
Damien Duff and Arjen Robben were key players, while Frank Lampard was given licence to roam forward and arrive late in the penalty area. The biggest secret to their success, however, was Mourinho's use of a 4-3-3. Most clubs still used 4-4-2, meaning Chelsea had a numerical advantage in midfield.
Key players and moments
Between them John Terry and Petr Cech created a remarkably strong defence, their leadership and constant tactical instructions keeping everyone in line. Lampard and Claude Makelele were just as important in midfield, playing in opposing roles that balanced each other out.
Beating Manchester United 1-0 in the season opener was a hugely significant moment psychologically, marking their arrival as genuine title contenders. But in such a steadily successful year, the most important result of all was the 1-0 defeat to Liverpool in the Champions League semi-final.
Carlo Ancelotti – 2009/10
What they achieved
The only Premier League and FA Cup double in Chelsea's history was won in Ancelotti's first season at the club, and having played entertaining football along the way it is surprising the era is not more fondly remembered.
After a disappointing 2008/09 season in which Luiz Felipe Scolari only lasted until February, Ancelotti's instant success came as a surprise. They won the league by a single point, beating Wigan Athletic 8-0 on the final day to secure the crown, before defeating Portsmouth in the FA Cup final six days later.
How they did it
Ancelotti has never been one for small details, instead creating a trusting relationship with his players while displaying a knack for the macro tactics. His stint at Chelsea was perhaps the best example of this, as his frequent shifting of the formation between diamond 4-4-2, 4-2-3-1, and 4-3-3 kept things fresh, but with few individual instructions Didier Drogba and Lampard excelled on instinct.
Both players recorded their best individual campaigns in a Chelsea shirt as the team scored 103 league goals. The Italian had created a friendly and fun environment, which released the players' most creative and carefree side. He was a hugely popular figure inside the dressing room, even if that relaxed approach explains why things began to fall apart the following year.
Key players and moments
The partnership between Lampard and Drogba reached its peak this season, although arguably the defining feature was the support work on the wings from Nicolas Anelka, Florent Malouda, Ashley Cole, and Branislav Ivanovic. Their movement and overlapping caused constant havoc for defenders.
Beating Man Utd 2-1 at Old Trafford April swung the title in their favour, a second-half Drogba strike separating the two sides. It was a result that signalled once and for all Chelsea were over their sticky patch in January, a victory that came after a 5-0 win and 7-1 win over Portsmouth and Aston Villa respectively.
Antonio Conte - 2016/17
What they achieved
Chelsea broke the Premier League record for most consecutive wins (13), most points (93), and most wins (30) under Conte, a huge shock given the season had begun with just three wins from six games. Their success in the months that followed was relentless, with a surprise FA Cup final defeat to Arsenal preventing a near-perfect campaign.
Conte's success was partly thanks to their lack of European football, which meant the Italian had an entire week to drill tactical instructions into the players. He is very much a details man, and unlike his rivals Conte had plenty of time to prepare for each league game.
How they did it
Conte's 3-4-2-1 formation, implemented after their second consecutive league defeat in September, was simply too original for anyone to get to grips with. Using a back three and wing-backs, their defence was remarkably airtight, a compression between the lines that chimed with what Mourinho had done a decade earlier.
The uniqueness of the approach was in how he used those inside forwards, at times bunching up to become dual number tens – crowding and overwhelming the opposition midfield – and at times spreading out to become traditional wingers. Eden Hazard, Pedro, and Willian were all superb for Conte.
Key players and moments
Diego Costa's 20 league goals might not be particularly impressive, but his ability to hold up the ball was a crucial part of Conte's scintillating counter-attacks. In defence, it was the reimagining of Cesar Azpilicueta as a centre-back that allowed Conte to shift systems. New signing N'Golo Kante also went from strength to strength, winning PFA Players' Player of the Year.
Having won the title by seven clear points there is no dramatic match to recall. However, the turning point came during the second international break, when Conte had two weeks to work on the 3-4-2-1 that had just ended a three-game winless run. On their return, the Blues beat Leicester City 3-0 and Manchester United 4-0, matches that would confirm Conte was onto something.
Conclusion
Conte's record-breaking achievements re-introduced a back three to English football and gave Chelsea one of their best ever Premier League seasons. However, his FA Cup final defeat in 2016/17 means Ancelotti's first year at the club ranks higher. After all, they played more entertaining football and the partnership between Lampard and Drogba is more iconic than anything under Conte.
However, despite winning more major honours, Ancelotti's 2009/10 pales in comparison to Mourinho's achievement in 2004/05. Context is key: winning the first title, and doing it with a revolutionary style of football in England, paved the way for everything that followed.
