Chelsea is the team (other than Manchester City) that capitalized on Manchester United's downfall from being Premier League dominants.Credit for the same goes to their internal changes and massive signings. There is something peculiar about Chelsea and their summer transfer window prior to that season. Each time the Blues have added more firepower to their squad, it has yielded massive results.Recalling Sturridge, Matić signing ahead of the 2009-10 season; Fabregas, Costa, Drogba before the title-winning 2014-15 season and lastly Kante, Marcos Alonso and David Luiz during the 2016-17 window. Enough to prove Chelsea's success during the transfer window to reflect on their season.I have chosen to join @chelseafc in 2016 as it has always been my priority. I want to thank the Management of the Club, the President and my agent for making this agreement possible. I am grateful to my teammates and to our amazing fans as the adventure continues. Common’ Chelsea pic.twitter.com/5hieULDX1L— N'Golo Kanté (@nglkante) November 23, 2018However, even the seventh richest club in the world (currently) couldn't manage to do all this without filling their pockets first. And luckily, the EPL outfit never fell short on that.Chelsea is one of the few clubs to have successfully off-loaded players. Which brings us to the topic of the day. Ranking the best 5 best sales in Chelsea history.#5 Juan Mata | Chelsea to Manchester United (£37.1 million) | 2014The versatile attacker from Burgos, Spain, broke Chelsea's club record transfer fee back in 2014. After falling out of Jose Mourinho's plans, Mata was deemed perfect for their domestic rivals — Manchester United.Mata was happy to leave Chelsea following less playing timeThough fate united both at Old Trafford a few years later, Mata's switch to Manchester earned him more playing time under David Moyes and the managers who followed.The fee earned from Man United was used by the Londoners to sign a bunch of budding talent from across Europe and fortify their bench. Kurt Zouma was a notable name amidst that.#4 David Luiz | Chelsea to PSG (£50m) | 2014The price tag of £50 million put by PSG for a defender sent waves across the transfer market. Chelsea couldn't deny a mouthwatering deal and had to let go of their centre-back who had played a total of 143 games for them.David Luiz's record of being the most-expensive defender was later broken by van Dijk and Harry MaguireMedia went into a frenzy over the transfer, with many claiming the deal to be 'over-rated'. Nevertheless, the Brazilian proved his worth by winning back-to-back domestic trebles with his new club in his first two seasons.In 2015, David Luiz scored a goal at Stamford that saw the London side find their exit in the Champions League round of 16. He earned lot of criticism after having celebrated in front of the away crowd, which was once, his home.David Luiz: "I was always very happy at Chelsea. And then the understanding of knowing that my cycle was over, even though I thought it wasn’t going to end that way, in a quick decision. I decided to leave Chelsea before I even had the door open at Arsenal." 👋 pic.twitter.com/OXwaT1Yb7z— Goal (@goal) April 17, 2020Despite the unfriendly gesture from both the ends, Luiz and the Chelsea loyals were happy to re-unite. Chelsea signed David Luiz back in 2016 for a fee reported around €35 million.