Tuesday's Champions League last-16 first-leg encounter will be the sixth time Diego Simeone has managed an Atletico Madrid side against Chelsea.

During his nine years at the club, the longest of any Atletico boss, Chelsea have appointed eight different managers.

And while Los Colchoneros are now thriving again, sitting top of La Liga even after Saturday's shock defeat by Levante, it was just 12 months ago that Simeone was being whistled by large swathes of the Wanda Metropolitano crowd, as Atleti limped to a 0-0 draw and were outplayed by 19th placed Leganes,

Renowned for building a team with grit and resilience, Simeone has revitalised Atleti with a new era of open, attacking football built around tactical tweaks and player role transformations, rather than a classic modern-day transfer window splurge.

In fact, many of Simeone's chief lieutenants sought pastures new with the departures of Antoine Griezmann, Lucas Hernandez, Rodri, Filipe Luis, Diego Godin and Juanfran in the summer of 2019, followed by the sales of Thomas Partey and Alvaro Morata last summer.

So how has Simeone reinvented Atletico and, with it, the perception of his own managerial style?

An overhaul in formation

For the vast majority of Simeone's tenure he had remained wedded to a staple 4-4-2 formation, characterised by defensive discipline and denying the opposition space between their compact lines.

It meant the forwards were relied on to provide the attacking threat.

In early November, after frustrating draws against Huesca, Villareal and Lokomotiv Moscow, Simeone made the bold decision to use three centre-backs in a 3-5-2 or a 3-4-3.

The immediate result was a resounding 4-0 win against Cadiz followed by a victory over Barcelona.

Atletico's record with this tactical setup has been superb - 18 games, 13 wins, three draws - and it has provided more goals, with 45 in La Liga this season already compared to 51 for the whole of the last campaign.

Three centre-backs has also seen a change to a more patient build-up of play - Atletico averaged 48.9% possession in La Liga last season, but 52.4% this season.

In Mario Hermoso, who fills the left-sided centre-back role, they have a very comfortable ball-playing defender, who often looks to pass through the lines and possesses a more expansive passing range, often switching play to the right side.
Atletico's centre-backs' passing comparison
Completed passes per 90 min
Mario Hermoso 57
Stefan Savic 45
Jose Gimenez 44
Felipe 30
La Liga only
Same players, new jobs

Simeone's old 4-4-2 approach required wingers and full-backs to remain defensively disciplined, but now the wing-backs in his new system are liberated to fly forward.

At left wing-back, speedy Belgian Yannick Carrasco has played a starring role in his second spell at the club, while on the right Kieran Trippier has been able show off his potent crossing ability (until his betting-related suspension).

Simeone has often paired this wide threat with two midfield 'number eights' in the 3-5-2 variation of his system.

Thomas Lemar had an unremarkable first two seasons in the Spanish capital, plying his trade on the left wing, leading to suggestions Atletico were looking to sell the Frenchman last summer.

Now, deployed in more central areas as a left-sided eight (or sometimes as a number 10), he has transformed his fortunes.

His control in tight spaces, speed and dribbling in this new role have effectively provided Atletico with a new profile of midfielder, one who can manipulate space for the progressive wing-backs.
Lemar's increased role in Atletico build-up play
Season Chances created per 90 min Touches in final third per 90 min Completed passes per 90 min
2019-20 0.6 19.9 31
2020-21 1.5 24.2 41.3
La Liga only

But perhaps Simeone's most intriguing transformation has been to the role of Marcos Llorente who, after being developed in the Real Madrid youth setup as a defensive midfielder, failed to impose himself in his natural position after crossing the inner-city divide in a move worth £27m in June 2019.

It was not until last season's Champions League last-16 second leg against Liverpool when a completely different type of player was unleashed, with Llorente substituted on to partner Joao Felix as a striker.

The change worked spectacularly with Llorente scoring a brace to help knock out the reigning European champions.

The Spaniard has gone on to register a remarkable 26 combined goals and assists in 34 starts since that night at Anfield, often appearing in more offensive positions such as a right-sided number eight (on the opposite side to Lemar), a second striker or more recently deputising at wing-back for the suspended Trippier and injured Sime Vrsaljko.
Life in Suarez yet and the £100m man

All of this has benefitted the evergreen Luis Suarez.

Dispensed by Barcelona in the summer, the Uruguayan has shown his former employers he is still as prolific as ever, with 16 goals in 18 La Liga starts.

The 34-year-old has added a clinical edge to Atleti's play, over-performing his La Liga expected goals tally by 4.81 goals, meaning he has scored almost five more goals than would be expected from the chances presented to him.

In contrast, Diego Costa and Morata under-performed by 1.85 and 2.98 goals respectively last season.

Similarly, Joao Felix, a player who had previously failed to match the expectations of his £100m move from Benfica in the summer of 2019, has started to flourish.

After starting only 28 matches in all competitions last season, due to injuries and a conservative system, this term he has been given more regular game-time in the front two (19 starts) and has already surpassed his combined goals and assists tally from last season with 14 compared to 12.

The Portuguese has shown pace to get in behind defences and a weight of pass to create chances, alongside a developing poacher's instinct, with eight of his nine goals this season coming from 12 yards or closer.
Yet still defensive Scrooges?

Interestingly, Atletico have still maintained their notorious defensive resilience, despite an overall more attacking style of play.

They have conceded just 16 goals in 23 league games, shipping 0.69 goals per game compared to 0.71 last season.

Simeone ensures his three centre-back system has balance; when one wing-back flies forward, the other often remains in a more disciplined position.

And Simeone has not been reluctant to sit deeper when ahead, with defensive midfielders Lucas Torreira, Geoffrey Kondogbia and Hector Herrera making 25 substitute league appearances between them this season, often entering the fray to help protect leads.

Overall, Atletico are significantly more well-rounded than when they knocked Liverpool out at the same stage last season, and will pose a genuine threat to Chelsea.