After completing a deal to send Diego Costa back to Madrid, Atletico and Chelsea meet in a massive Champions League encounter.
Atletico Madrid return to the Champions League after a dull 0-0 with Italian side AS Roma, looking to claim top spot in Group C after Chelsea hammered the weakest team in the group, FK Qarabag, 6-0. They have won their last three games in La Liga and sit in second position.
Chelsea's win over Qarabag has given their goal difference a helpful boost, and the Blues are third in the Premier League having gone unbeaten since their shock 2-3 loss to Burnley on the opening day.
Here is all you need to know ahead of Wednesday's match-up.
Atletico Madrid 2-2 Chelsea - Champions League (2009)
The two sides have met only twice at the Vicente Calderon Stadium, and both have unsurprisingly come in the Champions League. In 2009, Carlo Ancelotti's Chelsea fought for a hard-earned 2-2 draw to secure progress into the Round of 16.
Beneath the towering Didier Drogba here is a much younger-looking Sergio Aguero, who was just as lethal for the Spanish side as he has been for Manchester City. Both players scored a double in the match, with Aguero's 25-yard free kick saving a point in injury time.
Antoine Griezmann vs N'Golo Kante
Griezmann likes to operate as an attacking midfielder, backing up the likes of Torres and Correa as they lead the line. Much of the answer to restricting Atletico's attack is in clogging up the supply lines in and around the Frenchman.
N'Golo Kante will enter the pitch with words to this effect swirling in his head from Antonio Conte, so expect to see the two vaguely diminutive players involved in a series of duels.
Diego Godin vs Alvaro Morata
Diego Godin was rested for Atletico's 2-0 win over Sevilla on Saturday, and would meet a familiar face in the blue of Chelsea. With all of the discussion of Diego Costa and perhaps Fernando Torres as the strikers with a bit of history on both sides, Alvaro Morata's Real Madrid connection will not be be forgotten by the Spanish faithful.
Atletico's famously mean defence will come under an examination from Eden Hazard and Pedro as well, but Morata will endear himself much more to his new fans with a last minute winner against a world-beating side than a hat trick against Stoke.
Atletico may push Augusto Fernandez back into the squad, but Simeone will likely keep his duties to a minimum. Otherwise, they are at full strength.
Chelsea are waiting on the fitness of David Luiz, whose wrist was injured against Arsenal. Danny Drinkwater is still not ready for the Blues.
Predicted Atletico Madrid XI: Oblak, Juanfran, Savic, Godin, Luis, Saul, Thomas, Koke, Carrasco, Griezmann, Correa
Predicted Chelsea XI: Courtois, Rudiger, Azpilicueta, Cahill, Moses, Bakayoko, Kante, Alonso, Pedro, Hazard, Morata
Both sides are famed for their defensive capabilities, so it will be interesting to see which can open the other up in the attacking third. If N'Golo Kante can keep Antoine Griezmann quiet, it will be Chelsea who put the pressure on.
Three crucial points could be on the way in Chelsea's bid to make a serious dent in Europe this season.
Prediction: Atletico Madrid 1-2 Chelsea