Champions League goal glut a result of aggressive pressing in advanced areas
The most peculiar thing about Barcelona's astonishing 6-5 aggregate victory over Paris Saint-Germain wasn't the remarkable comeback itself, but the fact that it wasn't entirely out of keeping with the general feel of the Champions League round of 16.
Ten years ago it would have been ludicrous to imagine a come-from-behind win featuring seven goals. Matches at this stage of the competition tended to be tight, tense and tactical, with first legs often finishing 0-0; the opening games of 2006-07 round of 16 featured two goalless draws, as well as two 1-0 results and a 1-1.
But last week alone, alongside the Barca-PSG goal glut, we witnessed six goals at the Emirates as Arsenal were thrashed by Bayern Munich, and Dortmund stuck four past Benfica and there were four more in Italy as Real Madrid beat Napoli 3-1.
In fact, heading into Tuesday's game, there had been 55 goals scored in 12 knockout-round games, an average 4.58 goals per game. Suddenly, Champions League football is about all-out attack rather than solid defence. And in that context, the idea of Barcelona netting six times doesn't seem quite so crazy.
There hasn't seemed to be a particularly obvious pattern in these matches. A high goals-per-game average is often a sign of the vast inequality between two sides and while some ties, most notably Bayern's 10-2 aggregate victory over Arsenal, featured one clearly superior side, there have also been plenty of evenly balanced goalfests.
For example, Manchester City's 5-3 win vs. Monaco and Atletico Madrid's 4-2 triumph at Bayer Leverkusen were both that type of contest. Granted, each eventually had a clear winner, but the games were enjoyable, even battles between two sides capable of winning.
Several factors have contributed to the high-scoring contests. A high shot-conversion percentage is one reason in this particular round but, if there is one cause above the others, it is the rise of heavy pressing by teams in advanced areas of the pitch.
It has been notable, for example, that in the Leverkusen vs. Atletico, Man City vs. Monaco and PSG vs. Barcelona matches, at least one team has pushed up aggressively and made disrupting the opposition's play a key part of their game plan.
This doesn't necessarily cause a lot of scoring, though, and in the Premier League, where teams like Tottenham and Liverpool often seem better at pressing than anything else, it can lead to a scrappy, disjointed game. But the quality of football in the Champions League knockout round is higher and the pressing more integrated.
Many chances have come from a result of pressing; either a team has been aggressive and regained possession quickly to create an opportunity, as Barcelona did against PSG, or the press is broken quickly and the opposition race through toward goal, as Monaco did effectively in the first leg against Man City.
More than anything, this approach has created fast-paced, end-to-end matches. Throughout the 2000s, knockout rounds were played at a slower pace and essentially all about two teams sitting back and trying to work each other out tactically before slowly and methodically exploiting weaknesses.
The likes of Rafael Benitez and Jose Mourinho were the dominant coaches a decade ago whereas, now, that purely defensive style is considerably less popular.
Instead, coaches like Maurizio Sarri (Napoli), Pep Guardiola (Man City), Thomas Tuchel (Borussia Dortmund), Jorge Sampaoli (Sevilla) and Diego Simeone (Atletico Madrid) have made collective pressure a fundamental part of their playing style.
When it works, it's a great attacking strategy but, when it fails, it can go disastrously wrong. Either way, it usually prompts great entertainment when performed by talented players in cohesive systems.
Will this week's matches be quite so entertaining? Logic would suggest not. Sampaoli's Sevilla and Guardiola's Man City both have the advantage from the first leg and are travelling away from home, meaning they will more likely use a reactive strategy, slowing the tempo and/or playing on the break. They don't want an open game.
And can Tayfun Korkut's Leverkusen press to overturn a two-goal deficit at Atletico? With the Spanish side so dangerous on the break, it feels as if such an approach could backfire badly. Meanwhile, Porto aren't a side particularly renowned for their pressing, so it would be a surprise to see them playing that way at Juventus.
Regardless of the specific tactics involved, however, it felt as if the Champions League needed a round like this. Amid complaints the tournament is becoming frustratingly predictable and reports that viewing figures have dropped, a spark was needed.
It's difficult to say that the ties have not been predictable -- Bayern, Dortmund, Barcelona and Real are definitely through, with Juve and Atletico highly likely to join them -- but it has unquestionably been entertaining. Barca's comeback against PSG, for example, is surely among the most memorable games of the Champions League era.
It feels as if the competition's current state marks the third major era since the turn of the century. First were the defensive years, when teams sat back and played on the break, hoping take the lead and then defend their advantage.
Next came the possession era, featuring long spells of ball retention. Now, it feels as if that concept of "control" has become less valued, and playing in a more frantic manner to win possession and attack quickly is preferred.
It remains to be seen how long things stay that way. What is for sure, however, is that this approach is producing lots of goals.
Michael Cox is the editor of zonalmarking.net and a contributor to ESPN FC. Follow him on Twitter @Zonal_Marking.