MADRID -- How do you beat Liverpool? Just ask Diego Simeone, the coach who found a way to make Jurgen Klopp's Supermen look like a team of Clark Kents as Atletico Madrid claimed a 1-0 Champions League round-of-16 first-leg win at the Wanda Metropolitano on Tuesday.

Sometimes, old-school tenacity, organisation and a 4-4-2 -- that often-derided unimaginative formation -- can achieve what nothing else can. It all worked for Atleti, and their 1-0 win -- courtesy of Saul Niguez's fourth-minute goal -- has set up what promises to be a seismic second leg at Anfield next month.

Klopp had said in the build-up to this game that playing against Atletico is "one of the most difficult things as a footballer" and that "if you don't play at your very best, you have no chance." He was proved right, but if the Liverpool manager thought Atletico were tough to beat in this game, just wait until they turn up at Anfield with a lead to defend.

"I am fine," Klopp said after the game. "1-0 down at half-time, we have the longest half-time break and we will use that.

"Welcome to Anfield. It is not over yet."

Simeone and Atletico may not appeal to the purists, but there is still beauty in the way the team plays, if only for the rigid organisation and never-say-die spirit of the players in red and white stripes.

Sure, the final whistle in Madrid marked only the halfway point in this tie, and Liverpool will go into the return game as favourites to progress to the quarterfinals. But when Liverpool don't win a football match nowadays, it is big news, simply because they have become such an effective winning machine under Klopp.

Since lifting the European Cup for a sixth time, when beating Tottenham 2-0 at this stadium in last June's Champions League final, Liverpool have added the UEFA Super Cup and FIFA Club World Cup to their trophy cabinet. They have also built what is likely to be an unassailable 25-point lead at the top of the Premier League on the back of 25 wins in 26 games, drawing the other. But against Atletico, Liverpool ran into a wall of determination and defensive discipline -- as well as some typical Atleti belligerence -- and, all of a sudden, the best team in the world looked as human and vulnerable as everybody else.

Saul's goal, following Liverpool's failure to deal with an Atletico corner, was enough for the Spaniards, who went on to preserve Simeone's unbeaten home record in the Champions League by denying Klopp's men a single shot on target during the whole game. Just think about that. Not once did Liverpool, with the combined talents of Mohamed Salah, Sadio Mane and Roberto Firmino, force Atleti goalkeeper Jan Oblak into making a save.

It was such a frustrating night for Liverpool that Mane was substituted at half-time after being booked and escaping a red card for appearing to elbow defender Sime Vrsaljko. And then in the second half, Salah was taken off on 72 minutes after an anonymous performance.

But this wasn't simply Liverpool having an off night. This was an occasion when their opponents turned the screw so tightly that they could not find a way to cut loose and play their usual blistering attacking game.

And that was all down to Simeone and his players, who chased and tackled every Liverpool opponent, at times surrounding the likes of Mane and Salah with three defenders whenever they had the ball. They also made full-backs Trent Alexander-Arnold and Andy Robertson careless in possession and forced the pair into mistakes. Even Virgil van Dijk was made to look anything but flawless by the persistence of Argentine forward Angel Correa.

And it was all played out to a night of raucous noise, inside and outside the stadium, with Simeone conducting the crowd from the touchline and demanding more and more from his players as the game wore on. Klopp was quick to remind Atletico after the game that they must yet overcome the experience of playing at Anfield before thinking about winning this tie, but such is the mentality of Simeone and his players that it is difficult to envisage them collapsing in front of The Kop as the likes of Barcelona, Roma and Manchester City have in recent seasons.

Atletico will relish the opportunity to go there and spend 90 minutes resisting a Liverpool onslaught, throwing their bodies in the way of everything to get the result. They will break up play, commit technical fouls, hound Liverpool's players and make it an ugly encounter. They will pose a unique challenge to Liverpool, and the prospect of a fit-again Diego Costa offering Atletico an attacking outlet, as well as adding to the siege mentality, will make life only more difficult for Klopp's men.

As Klopp said, this tie is not over yet, but there is a distinct impression with Atletico that, rather than fear Anfield, they will actually be motivated by the prospect of dethroning the European champions there. Get set for another pulsating European night at Anfield, but the story might be a different one this time.