Liverpool really did lose a football match, do not adjust your screens.

The Reds haven't lost a single game in the Premier League this season, astonishingly winning 25 fixtures and drawing just once, and are well on track to overtake Arsenal's 'invincible' record.

However, that doesn't mean that Liverpool haven't put a foot wrong in other competitions and it's easy to forget that Jurgen Klopp's men have actually lost four times across 2019/20.

Losing the Community Shield to Manchester City is pretty trivial and so is the 5-0 defeat at Aston Villa where the Reds played their youth team, but the same can't be said in the Champions League.

The Reds made a poor start to the defence of their title with a 1-0 defeat at Napoli and now they need to turn things around at Anfield after losing by the same scoreline to Atletico Madrid.

Tactical analysis of Atletico 1-0 Liverpool

And while Liverpool fans are justifiably confident of a comeback on Merseyside, the performance of Diego Simeone's team leaves a blueprint for others to overcome the Premier League leaders.

So, how did they do it? Well, YouTuber 'Atlantis Football' has decoded some of the Atletico tactics on the night and has released a video explaining 'Simeone's defensive masterclass.'

Check out the full video down below, but keep scrolling for our break down of the tactics - targeting players like Trent Alexander-Arnold and Roberto Firmino - that are highlighted in the analysis.

Prepared for the Firmino threat

The midfield four of Koke, Thomas Partey, Saul Niguez and Thomas Lemar sat incredibly narrow.

It could have been easy for Firmino to find space between a midfield two when the ball was switched from side to side, but Partey and Saul were incredibly positionally aware.

They moved across the pitch to cut off the passing lane to Firmino when either Jordan Henderson or Georginio Wijnaldum had the ball, essentially isolating Sadio Mane and Mohamed Salah in turn.

Nullifying Alexander-Arnold

Because Simeone was focused on smothering Firmino, Atletico had to be content with Liverpool playing the ball out wide to Trent Alexander-Arnold in particular as they bombed forward.

This forced Alexander-Arnold to resort to crosses into the box, playing into the hands of Atletico's centre-back partnership of Felipe and Stefan Savic, who are positionally and aerially strong.

And they anticipated these crosses to an extent that they immediately dropped deep, ensuring that any deliveries into the box would be head-height, as opposed to foot-height, for Mane and Salah.

Smothering Liverpool's build-up play

Simeone made a key decision early in the game after noticing that Liverpool's defenders were easily progressing the ball to Fabinho from the back.

Saul was instructed to press high which, along with Alvaro Morata and Angel Correa swarming around goal-kicks, stopped Liverpool from playing centrally through their defensive third.

This married perfectly to the tactics applied to Firmino by forcing Liverpool out wide once again, ensuring the bull was funnelled to Andrew Robertson and Alexander-Arnold if in doubt.

Closing down space between the lines

Above everything, though, it was Atletico's ability to manage space that nullified Liverpool the most.

Whenever Henderson or Wijnaldum moved behind the midfield four, the Atletico players remained disciplined and focused on blocking off the passing channels as opposed to being drawn into man-marking.

The point? You guessed it... to stop Liverpool from playing through the middle.

And even when Liverpool switched to a 4-2-3-1 with Divock Origi as their vocal point, Atletico ensured that any knockdowns wouldn't fall at the feet of Firmino for a quick transition into attack.

Could other teams replicate it?

So, don't get it twisted, even 'invincible' teams are beatable.

There's no doubting that Atletico had the advantage of sitting back on an early goal, but Simeone still made some crucial tactical changes to neutralise Liverpool like so few teams have.

If you combine the right amounts of skill and luck, then it seems as though Liverpool might lose more games than expected. Then again, Klopp's team make a living out of proving people wrong.