It is always fascinating when polar opposites collide.
In the Premier League, Pep Guardiola's methodical Manchester City are leading the way, up against the juggernaut of Jurgen Klopp's Liverpool.
While Guardiola and Klopp are by no means cut from the same cloth, they do share similarities in their approach; relentless pressing, rapid counter-pressing and machine-like efficiency.
Yet in Diego Simeone, it is difficult to imagine an elite-level coach that contrasts with Guardiola quite so much. On Tuesday, we will see just how the styles match up.
It has been almost six years since a team coached by Guardiola went up against Simeone's Atletico Madrid, when Bayern Munich faced Los Colchoneros in the Champions League semi-finals.
Simeone triumphed on that occasion, albeit on away goals. Atleti went on to lose to city rivals Real Madrid in the final, while Guardiola has only been further in UEFA's competition once since then – last season, when City lost to Chelsea in the final in Porto.
Indeed, only three times in total have Simeone and Guardiola gone up against each other. Pep holds the edge in terms of wins (at least on the night), 2-1, with his Barcelona side seeing off Atleti 2-1 in LaLiga in February 2012, during his final season at Camp Nou.
Another two games will be added to that head-to-head record over the coming weeks in a Champions League quarter-final tie that represents a true clash of styles.
Possession obsession
Guardiola's death by a thousand cuts approach has yielded unprecedented success. City are a joy to watch at their best. Slick, swift, sublime. Everything you would associate with a team at the very top of the game.
As has been the case throughout his managerial career, Guardiola wants to dominate possession, control the opposition by simply not allowing them to have the ball and, if they do have it, then you can bet his team will win it back within seconds, or commit a timely foul (Fernandinho, anyone?).
Just taking this season into account, City average 66.9 per cent possession across all competitions, while they have attempted 30,155 passes, completing 27,067 (at an average of 601 successful passes per game).
Simeone is far less concerned with his side having the ball, but instead the focus is on staying compact and robust defensively, drawing a mistake – a stray pass, a heavy touch – out of the opposition and pouncing. And in relative terms, his approach has been just as successful.
Not that this is Simeone's approach across the board. Atleti have played some wonderful football during his tenure too, and had some sensational attacking players. Indeed, their current frontline options of Joao Felix, Luis Suarez, Antoine Griezmann, Angel Correa and Matheus Cunha is the envy of most teams.
Yet this season, Atleti average only 48.8 per cent possession across 41 matches. They have completed 14,533 passes, with 7,317 of these coming in the opponents' half. In comparison, City have registered almost 16,000 successful passes in opposition territory.
However, the difference is not so stark when it comes to balls played into the box, with City's 1,730 accounting for 11 per cent of their passes in the opposition half. That value jumps to 16.5 per cent for Atleti (1,209).
Simeone's men get a higher proportion of their passes in the other team's half into the area, though City have had 1,870 touches in the opposition box, with Atleti managing 964.
In the league alone, City have had 715 sequences involving 10 or more passes. In LaLiga, Atleti have had just 278.
City's possession does, of course, lead to shots – 837 of them this season in total. That dwarves Atleti's 490, though the Spanish side do have a better conversion rate (14.7 compared to 13.5).
Fierce off the ball
One similarity when it comes to Guardiola and Simeone is their desire to be aggressive in their approach to winning the ball back. While Guardiola's team will swarm an opposing player, Simeone's men will be tenacious and full-blooded.
So far this season, Atletico players have gone into 4,263 duels, while City have attempted 3,848. However, the success rate is closer, with the Spanish champions winning 52 per cent, and City 51.1.
Another major difference, however, is how City press.
In the Premier League, only Liverpool (354) and Brighton and Hove Albion (290) have forced more high turnovers than City (285), and Guardiola's side rank second when it comes to the average starting distance of their attacks from their own goal (45.1 metres).
When it comes to passes allowed per defensive action (PPDA), a measurement to quantify the extent and aggression of high presses, City rank joint-second, along with Liverpool, in the Premier League, with their 9.9 only bettered by Leeds United's 9.5.
Atleti's 207 high turnovers ranks ninth in LaLiga. However, their seven goals from direct attacks is joint-best in Spain's top tier. City have scored four times from such breaks this term.
Solidity comes first
This season, admittedly, Atleti have been unusually sloppy at the back, conceding 50 times and keeping 12 clean sheets, which is 17 more and 10 fewer than City, respectively.
Tracked over the previous five full seasons, however (since Guardiola joined City in 2016), only once have Atleti conceded more times than City, in 2018-19 (44 to 39).
Guardiola's teams take more risks in possession and City have made 42 errors leading to goals across his time at the club. It's been worth the pay off, but Simeone's more conservative approach has yielded just 21 such mistakes in the same timeframe.
Defensive grit is the bedrock of Simeone's success, and since the start of 2016-17, Atleti have kept 144 clean sheets. Yet, it is City who top the charts across Europe's top five leagues, with an outstanding 152.
Given City have scored 113 goals already this season – 41 more than Atleti – perhaps this quarter-final will not quite be as even as it might have been in seasons gone by, and it is the side from Manchester who must be considered favourites.
But, as proved with their clinical display at Old Trafford in the round of 16, Atleti still have the ability to frustrate and pick their moments to shine in attack.
This is further evidenced by Atleti's LaLiga-leading expected goals (xG) differential of +8.5 this season. In stark contrast, City have scored 6.2 goals fewer than the quality of their opportunities would have suggested.
However the tie plays out, it is sure to be an enthralling tussle.