Stop Messi, stop Barcelona. It’s not that simple for Liverpool.

Lionel Messi is the best player in the world, but Liverpool should be optimistic about their chances against Barcelona.

Stop Lionel Messi, stop Barcelona.

That seems to be the challenge facing Liverpool as they prepare for the first leg of their Champions League semifinal against Barcelona on Wednesday. The good news is Messi is only one player. The bad news is the one player he is is Messi, possibly the greatest player of all time.

The even worse news is that this specific version of Messi is harder to stop than any of those that preceded him. This is because, at this stage of his career, he no longer really has a position. Or rather, he plays every attacking position at once.

And so to present this as Messi-Andy Robertson duel or a Messi-Virgil van Dijk duel would be both to completely ignore the way Messi plays now and, frankly, to significantly overestimate any individual player’s ability to contain him one-on-one.

If Barca are able to isolate their captain against any of Liverpool’s players with any sort of consistency, they’ll be confident of advancing to their first Champions League final since they won the competition in 2015.

This is not, it’s important to acknowledge, necessarily because he’ll beat that player one-on-one (van Dijk, of course, hasn’t been dribbled past once this season, and he’s played against some extraordinarily good dribblers — Neymar, Kylian Mbappe, Eden Hazard, etc.). It’s because if Messi is one-on-one against anyone, it means he’s in space. And if Messi’s in space with any regularity, well, goodnight.

One of the things that sets Messi apart is his decision making. He picks the best option, always. If he dribbles through four players, it’s because there were no better passing options. If he plays a 40-yard no-look through ball between your center-back and right-back to an overlapping Jordi Alba, it’s because one of them lost track of Alba’s position. Even if he’s doing nothing, standing still on the right touch line, he’s learning something about how to beat you — if not in the first leg, then in the second.

This is the problem with the “stop Messi, stop Barcelona” theory. Stopping him is tantamount to stopping an entire team, both because he plays in so many different positions at once and because, contrary to what some Ernesto Valverde critics are prone to suggest, Barcelona are not a collection of 10 donkeys plus Messi, but a team of 11 elite players whose task is to get the very best out of one transcendent one.

If you draw up a plan to stop Messi from the right wing, he’ll move into the center. If you draw up a plan to stop him there, he’ll drop deep and dictate play from midfield. If you draw up a plan to stop him everywhere on the pitch at once, you’ll find out the hard way that Barcelona are not, in fact, a one-man team, and you’ll watch Luis Suarez or Ousmane Dembele or Philippe Coutinho or Ivan Rakitic or Alba or Sergio Busquets beat you instead. (Liverpool, of all teams, should know what Suarez and Coutinho are capable of on their own.)

What, then, are Liverpool to do?

There’s no stopping Messi, but Jurgen Klopp’s side can certainly contain him. And this is simply a matter of hard work, concentration and, perhaps most important, defensive awareness.

Robertson will often be the closest Liverpool player to Messi, who still spends more time out on the right than anywhere else. Other times it will be van Dijk or Fabinho. Other times still it will be whoever plays on the left of the Red’s midfield three (probably Naby Keita or Georginio Wijnaldum; possibly James Milner). On rarer occasions, it might be Joel Matip or Trent Alexander-Arnold. (If you’re keeping count, that’s every player on Liverpool’s team except the front three, and Sadio Mane should probably be prepared to track back a little more than usual as well.)

Whoever it is, what’s important is that he receives help immediately when the ball is played toward Messi, preferably to his (the defender’s) right. Messi’s first instinct is always to look to his left. In an ideal scenario for Jurgen Klopp’s side, as soon as he does this, a Liverpool player will arrive in front of him, cutting off the early pass, and forcing him to dribble backward before he can dribble forward.

Finally, they must be prepared to foul, and foul intelligently, and then hope Messi doesn’t score from the ensuing free-kick.

Messi, then. Pretty good player.

As good as he is, however, and as tempting as it is to reduce this tie to what he can do (and how to prevent him from doing it), there are a lot of reasons for Liverpool to be confident of advancing to their second Champions League final in as many seasons.

Klopp has built an extraordinarily good team, capable of playing in a variety of ways — sitting deep and playing on the break, controlling the ball to break down deep-lying opponents or creating chaos and dominating in transition.

Against Barcelona, it seems likely they’ll opt for some combination of the first and the last of those three options. It seems hard to imagine Barca won’t dominate possession in this tie. Valverde isn’t Pep Guardiola, but that’s still his team’s natural instinct, and controlling the ball, slowing the tempo of the game, is one way to limit Liverpool’s threat on the counter.

Liverpool, of course, are experts at baiting their opponents into playing passes into dangerous areas, winning the ball back quickly when they play those passes and then letting Mane, Mohamed Salah and Roberto Firmino get to work. Given the supreme technical quality of so many of their players, this is a tactic Barca are likely to be susceptible to. Sergio Busquets isn’t going to shy away from a dangerous, high-risk pass between the lines because he sees Jordan Henderson lurking. He’s too confident in his own ability to execute difficult passes (as he should be).

And so the deciding factors in this tie (outside of Messi) is likely to be, on the one hand, how effectively Barca can execute those sorts of passes and, on the other, how effectively Liverpool can win the ball back when Barca play them.

The reason these moments project to be so important is Barcelona’s transition defending, which is, at the risk of underestimating some of the Europe’s most accomplished midfielders, Quite Bad.

Despite another exceptional season for Gerard Pique, and an impressive run of form by Samuel Umtiti stand-in Clement Lenglet, the team overall has deteriorated defensively over the past two seasons. In 2017-18, they conceded 41.62 xGA in their 38 Liga games. This season, through 35 games, they’ve conceded 40.02 xGA, which puts them on pace for a five-year high (as far back as Understat’s records go). In three seasons before that, their worst xGA total was 34.03, in 2015-16.

The eye test backs this up. Barca routinely go through spells, as they did once more in their title-clinching win against Levante on Saturday, when they seem completely overrun in midfield, only to be bailed out by poor opposition finishing or the superb Marc-Andre ter Stegen.

There’s an at least superficially persuasive argument to be made that this is simply a product of the fact they’re so far ahead in La Liga, and so are prone to, let’s say, lapses in concentration. Against a team of Liverpool’s caliber, they’ll presumably take more care with the ball and won’t expose themselves so much without it.

There’s certainly some truth to this. Barcelona haven’t allowed more than 0.6 xG in any game of their four Champions League knockout round games so far, an impressive number even if their opponents, Lyon and Manchester United, weren’t nearly as good as Liverpool.

But even so, it’s hard to look at Barca’s midfield and not feel slightly worried about their ability to stop Liverpool’s counter-attack. Busquets is a treasure, but these days he’s a very slow treasure indeed, and the ability to read the game can only get you so far when your 100 meter dash time is 15 seconds. He improves Barca’s attack significantly, but there are real defensive questions marks.

He’ll likely be supported on Wednesday by Arthur, who has had an excellent first season in Catalonia, but whose strength is his ability to keep the ball, set tempo, control the game. It’s hard to say how he’ll fair against someone like Henderson, less technically skilled but a relentless worker and physically dominant in 50-50s.

Rakitic is probably better suited to a physical, transition-heavy game, but he won’t be able to compete with three physical Liverpool midfielders by himself. Given this, it’s tempting to wonder whether Valverde might start Arturo Vidal to add some extra muscle to his midfield. It seems hard to imagine him doing this in the home leg, but the Chilean could be a useful player at Anfield next week.

Finally, we must say a word about both teams’ full-backs. Alba is one of Barca’s most dangerous attacking players, and Messi prefers no pass more than the lofted through ball to Alba cutting inside behind the opposition right-back. Alexander-Arnold has improved significantly this season, but if there’s a weakness in his game, it’s tracking exactly those sorts of runs. With Salah playing ahead of him, he doesn’t get the same defensive cover as Robertson on the opposite wing, and he’ll have to display a level of defensive sharpness he occasionally lacks when Liverpool are playing inferior teams.

Sergi Roberto (who seems likely to start ahead of Nelson Semedo) has a different, more defensive role than Alba, and will be particularly important in those transition moments. He’s capable of stepping into midfield, as he’s likely to have to do on occasion to slow down Liverpool’s counter-attack. He can’t, however, ignore the traditional right-back position, which is where Robertson does so much damage for this Liverpool attack.

Robertson may be tempted to sit a little deeper than usual to help defend Messi, but there could be significant rewards if he’s willing to get forward as much as usual. Messi provides almost no defensive cover, and Sergi Roberto often drifts inside to support his midfielders, meaning there could be a huge amount of space down Barca’s right. Robertson has 11 Premier League assists so far this season, and is one of Liverpool’s key creative players. With all the elite forwards on the pitch in this tie, he is the difference-maker most likely to be ignored.