It isn't just that Atletico Madrid beat then-Champions League champions and current Premier League champions Liverpool, it's the way they did it. After grabbing a very early goal in the first leg, Atletico spent the better part of two whole games frustrating the Redmen, partially by keeping players like Roberto Firmino and Mo Salah contained, mostly by keeping men behind the ball and chipping away at niggling fouls.

That is to say that the lesson to be learned from the Round of 16 isn't that Atletico Madrid beat the team considered the best in the world, it's that they have absolutely no scruples about the methods used to do it. There was no attempt to outplay Liverpool, only to beat them – first into submission, then on the scoresheet.

This, according to manager Diego Simeone, changed the team's fortunes this year. Having lagged behind the top boys of La Liga – Real Madrid and Barcelona – all year and struggled for draws against worse teams, the Liverpool win on March 11 this year convinced Atletico they could beat the side considered best in the world and have not lost since.

More importantly, it seems unlikely to go against their rivals tonight at the Estadio Jose Alvalade in Lisbon, Portugal. Red Bull Leipzig could be considered a lesser version of Liverpool. Manager Julian Nagelsmann loves free-flowing attacking football in a similar manner to Liverpool's German manager Jurgen Klopp, and it's served his side well as they have only lost once – a 2-0 defeat to Borussia Dortmund – in their last 15 clashes.

They're a young and talented side looking to make an impact and have already excelled in this year's tournament. In 2017/18, they were a filler side and got sent to the Europa League after coming third in the Group Stage behind Besiktas and Porto. Now they're in the quarter-finals after topping the Group Stage and defeating last year's runner-up Tottenham Hotspur 4-0 on aggregate.

They're the type of team an evil genius like Simeone enjoys dismantling. In a prematch interview, he's already talked about how he wants to "(take) the game in the direction we want it to go and look to hurt our opponents." If he does, he will be late as the coronavirus has already beaten him to the punch.

Had this game taken place when initially scheduled, RB Leipzig would still have their best player, Timo Werner. Instead, he has already completed his transfer to Chelsea. They will be more reliant than ever on the wingers Emil Forsberg and Marcel Sabitzer, who combined still scored eight less goals this season than Werner.

As for Atletico, the coronavirus has been more hands on. Angel Correa and Time Vrsaljko both tested positive for COVID-19 earlier this week and are currently undergoing self-isolation. Physically, their absences probably won't be missed as Simeone has plenty to choose from at the right-wing and right-back positions, respectively; mentally, however, it may take a toll. UEFA has put in a lot of work to ensure these games can take place safely, and for two players from the same team to still get infected, it shows nobody is truly safe amidst this pandemic.