The Brazilian dynamo, still yet to complete formal personal terms, will be Chelsea's third major signing of the summer after previously adding Diego Costa and Cesc Fabregas to the ranks.
With Thibaut Courtois returning from a loan spell at the Vicente Calderon to mind the sticks in West London, a strong Colchoneros/La Liga presence will be felt throughout this Blues side for the 2014-15 season.
Despite acquiring three world-class players in addition to the January haul of Nemanja Matic and Mohamed Salah, Chelsea's net spend is close to just £40 million following the astronomic sales of Juan Mata and David Luiz in the last six months.
Jose Mourinho is working the transfer window superbly.
Given his age (28, turns 29 in August), Luis isn't quite the steal Matic was. The Guardian speculate he will cost the Blues between £15-20 million. Nevertheless, his transfer represents an absolutely excellent piece of business.
Ideally, he will come in as the first-choice left-back and take the reins from stand-in wrong-sider Cesar Azpilicueta. The Spaniard can then move to his natural right-back slot and compete with Branislav Ivanovic for a place in the XI.
Luis was a top-three left-back in world football over the course of the 2013-14 season and is arguably the most complete of them all. His remarkable engine and combination of defensive and attacking skills make him a general all-rounder, and he's comfortable in every area of the pitch.
He tucks in expertly when his centre-back asks him to, defending his corner well. Last season, he averaged 4.1 tackles per game, per WhoScored.com. Many of those were in his own third.
Considering his side won the league and scored 77 goals in the process—suggesting Atletico were not under the defensive pressure a relegation-threatened side would be—his tackle rate is absurd.
He defends first, unlike many modern full-backs, and that's a trait Mourinho will take delight in.
Going forward, he links extremely well with a winger, and the chemistry he strikes up with his partner at Chelsea—likely Eden Hazard—could be the key to making this transfer a resounding success on every level.
He's not an assist machine like Ricardo Rodriguez, but his aggressive positioning makes him an impactful player in the final third. He rarely loses the ball, with just 27 dispossessions tracked from 32 Liga starts last year, making him an economic and safe pair of feet to utilise moving forward.
In a market where Rodriguez and Alberto Moreno represent can't-miss prospects but still offer up slight possibility of failure, Luis is the safest bet of all.
He plays like a European, not a South American. While that may have stopped him from making Luiz Felipe Scolari's FIFA World Cup 2014 squad, it likely points to an immediate settling and finding of form in England.
After waving goodbye to long-standing hero Ashley Cole, this is exactly the sort of replacement Mourinho and Chelsea needed.
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