The Blues ended Jose Mourinho's first season back at Stamford Bridge without a trophy, but the club showed progress from their time under Rafael Benitez. Now, with the transfer window upon us, Chelsea are expected to spend heavily to make a real push at winning the Premier League title next season.
A number of big name stars have been linked with switches to West London, but three of the main names associated with transfers to Chelsea are Atletico Madrid trio Filipe Luis, Tiago and Diego Costa. All three played key roles as Diego Simeone's side clinched their first La Liga title since 1996, whilst they also went on an incredible run to the Champions League final - including dumping Chelsea out in the semi-finals.
It seems that their performances against Mourinho's men may have made the Chelsea boss sit up and take notice, with strong speculation that all three will be Chelsea players sooner rather than later - but which one will be most important to Mourinho's Chelsea?
Replacing the long-serving Ashley Cole has to be a priority for Mourinho, and whilst Cesar Azpilicueta filled in well at left back, he's better suited to the right hand side of the Chelsea defence. Adding Brazilian Luis gives them an experienced player who excels going forward, and has the energy to get up and down the left flank - just as Cole has done so well for Chelsea.
Meanwhile, Tiago would be returning for a second spell at Stamford Bridge after Mourinho signed him from Benfica back in 2004. Now 33, the Portuguese midfielder offers vast amounts of experience and composure in the middle of the park - which Chelsea need to add alongside Nemanja Matic after the departure of another Blues legend, Frank Lampard.
But the most important signing would be Brazilian-turned-Spanish striker Costa. Chelsea struggled massively up front last season, with Samuel Eto'o, Demba Ba and Fernando Torres all struggling to put together consistent displays in front of goal - which ultimately cost them the title.
Instead, Costa would bring his sensational record of 35 goals in 44 appearances this season to Stamford Bridge, and he has all the talent - and character - to be the perfect striker for Mourinho's men.