Since Roman Abramovich bought the club in 2003, Chelsea have seen their fair share of players come and leave the club. Among them, legends have been born and history written, but as is natural with so much money, there have also been a number of very high profile transfer flops.
What follows is a list of five of the best and worst purchases in the Roman Abramovich era.
When choosing who must go on the list, it was much harder to pick the best five than the worst five. Although the biggest transfer failures have been well-publicized, there have been far more successes. So many in fact, that some notable omissions include Joe Cole, Arjen Robben, Michael Essien, Michael Ballack, Branislav Ivanovic and Eden Hazard.
The reason for this is that the top five have been chosen with special consideration for value for money, impact on the club and length of stay. Ivanovic and Hazard have not been included because they are still at the beginning of their Chelsea careers, and have much more history to make.
As for the flops, the same sort of considerations were made, especially money. You may notice that a certain Fernando Torres is absent from either list—and that is because the jury is still out on the Spaniard. Also absent are some players such as Yuri Zhirkov, who, although he did not stay long, left for a respectable fee.
So without further ado, here are the best and worst of Chelsea's transfers from the last ten years.
Veron was a curious transfer at the beginning of Abramovich's reign.
The Argentinian had struggled to make an impact since joining Manchester United, and might have been worth a gamble if he could be signed for a good price.
Claude Makelele made such an impression at Chelsea, that they named a position after him.
Sitting right in front of the back four, Makelele protected the defense, and started many plays from the back of the pitch. He consequently had a crucial part to play in both of Chelsea's Premier League title victories under Jose Mourinho, and left the club a fan favorite in 2008.
Mutu started his Chelsea career in the best possible fashion, scoring four goals in three matches. But the striker's form soon declined, and Mutu started scoring less and less.
After almost 10 years at Stamford Bridge, Petr Cech might just be one of the best signings in Chelsea's history, let alone the last 10 years.
His record 21 clean sheets in 04/05 and just 22 goals conceded in 05/06 were instrumental in Chelsea's dominance throughout that period. Still just 31-years-old, Cech could potentially be Chelsea's number one for 10 more years.
Yet another attacking flop, Hernan Crespo arrived for almost £17 milion and struggled to get comfortable in the Premier League, leaving on loan after just a year.
Although he returned for the title-winning 05/06 season, he was always overshadowed by Didier Drogba, and soon left once more.
When a player's career at a club ends as magnificently as Didier Drogba's did, it can be easy to forget how slow it started.
It wasn't until Drogba adopted the no. 11 shirt in the 06/07 season that Drogba became the goal machine that he was by the time he left the club.
Scoring 33 goals in all competitions, that total was more than his first two seasons combined. Drogba memorably finished his Chelsea career with the Champions League-winning penalty, and will be forever ingrained in Chelsea legend.
Despite arriving in a cloud of scandal, Ashley Cole has been an incredible addition to Chelsea's first team since his transfer in the 06/07 season.
Having recently won the Champions League with Chelsea and reached 100 caps for England, few can match the achievements of Cole's career.
Despite being 32-years-old, Cole is still widely considered to be one of the best—if not the best—left-backs in the world.
And all for £5 million plus William Gallas? Bargain.
With that £30 million price tag, Andriy Shevchenko was always going to fail at Stamford Bridge, as expectations could surely never be met.
But Shevchenko never even managed to quietly fit in, scoring just four Premier League goals in his first season, and five the season after.
Although newer players such as Hazard have not been included, this list would not be complete without Juan Mata.
The Spanish midfielder has been the heartbeat of the team since his arrival two years ago, being voted Player of the Season both years, and looks set to turn into a bona fide Chelsea legend in no time.