The 2018 Champions League semifinals are less than 24 hours away. The two ties, Bayern Munich vs. Real Madrid and Liverpool vs. Roma, are intriguing for different reasons. There are reunions and grudge matches, points to prove or disprove, historical trends to extend or overturn, and fascinating tactical questions.

All of those appear among our nine storylines to watch heading into the semifinals:

NINE CHAMPIONS LEAGUE SEMIFINAL STORYLINES

1. Munich, Madrid, and the Champions League Clasico

Can we call it that? Yeah, we’re going to call it that. Because no two clubs have met more often in the Champions League, and no two clubs have been more evenly matched. Over 24 all-time meetings, it’s Bayern Munich 11, Real Madrid 11, and two draws. Real Madrid has won six of the 11 knockout round ties; Munich has won five. It’s 37-36 to Real on aggregate. Historically, the matchup could hardly be tighter.

2. Real has won more Champions Leagues than the three other semifinalists combined

Madrid leads the way with 12 European titles. Bayern Munich and Liverpool have five apiece. Roma has never won any European competition.

And the odds for the 2018 title should probably reflect history, albeit with tighter margins. Real is an ever-so-slight favorite over Bayern in the semis, and therefore an ever-so-slight favorite to lift the trophy in Kiev, with Munich and Liverpool – the most likely finalist – right behind the reigning champs. Roma brings up the rear.

3. Zinedine Zidane’s tactical conundrum

Real Madrid has danced past PSG and Juventus without really ascertaining what exactly its best 11 is. The obvious answer would be the exact same 11 that ripped Juve apart in the quarterfinal first leg in Turin. But that same 11, with one like-for-like swap each in attack and defense, was woeful and problematic in the second leg. And a different 11, with Lucas Vazquez and Marco Asensio introduced as defensively disciplined wingers in a 4-4-2, saw Madrid through against both PSG and Juve.

Madrid’s main problem in the established 4-3-1-2, with Toni Kroos and Luka Modric beside Casemiro, and Isco in front of them, is its defensive fragility in wide areas. Kroos’ and Modric’s responsibilities are primarily attacking. Marcelo and Dani Carvajal, the fullbacks, love to get forward. That leaves loads of space on the wings and in midfield half-spaces when Real loses possession.

And those are areas in which Bayern Munich has feasted throughout this decade. Five years ago, or perhaps even one year ago, the dynamic right-sided duo of Arjen Robben and Philipp Lahm would have surely compelled Zidane to field at least one of Asensio or Vazquez. A Franck Ribery-David Alaba combo on the other side might have brought both into the fold.

But Lahm has retired; Robben isn’t the player he used to be; neither is Ribery. Jupp Heynckes might have to slot Thomas Muller in as his nominal right winger to get the German forward in his team. So is Munich’s wing threat still fierce enough to provoke a reactive approach from Zidane? Or will the Madrid manager stick with his tried and probably-still-trusted 11? The answer could define the tie.

4. Sergio Ramos’ escape

Madrid can effectively play seven attack-minded players when it has Ramos – still, at 32, one of the best, most mobile and most versatile center backs in the world. But when Ramos doesn’t play because he’s accumulated more yellow cards than any other player in Champions League history? That’s when things get hairy – that’s when they got hairy against Juventus.

And after the Juve second leg, there were reports that Ramos would miss the semifinal first leg because he came down to field level while serving his quarterfinal suspension. His absence might have prompted Zidane to lean toward his 4-4-2 away from home. But Ramos has avoided an additional ban. That’s the biggest news ahead of the semis, because Raphael Varane and either Nacho or Jesus Vallejo would have had a nightmarish time trying to contain Robert Lewandowski and track Muller’s sneaky runs underneath.

5. Bayern Munich’s midfield puzzle

Behind Lewandowski, and in front of his back four, Heynckes has selection questions of his own. He’ll line up in some form of a 4-3-3/4-1-4-1/4-2-3-1, but he could play any five of eight options. He has Robben, Ribery, Muller and James Rodriguez as wingers. He has Muller and James as possible No. 10s in a 4-2-3-1. He has Javi Martinez, Thiago Alcantara, Corentin Tolisso and Sebastian Rudy as central midfielders.

With Arturo Vidal out for the season due to injury, Martinez and Thiago would appear to be must-starts. Muller probably is as well. He and Thiago, regardless of where in the formation they play, will probe and exploit those aforementioned half-spaces behind Kroos and Modric.

But that leaves two spots up for grabs. Will Heynckes bring in Tolisso – whose been battling a minor injury – to firm up the midfield in Vidal’s absence? Or will he play Muller centrally in front of Martinez and Thiago, with two true wingers flanking him? The latter option might be defensively inadequate. But it would maximize the talent on the pitch. So it’s probably Heynckes’ best option for the first leg at home.

6. The importance of Virgil van Dijk

Let’s pivot to the other semifinal, which in a former world might project as a goal-fest. Six months ago, the thought of Dejan Lovren, Joel Matip and Simon Mignolet up against Edin Dzeko, Diego Perotti and company would have been frightening. Dzeko in particular would have been a handful for the Reds.

But now? Virgil van Dijk might as well have been signed specifically for this matchup.

Before van Dijk arrived in early January, Liverpool was conceding 1.14 goals per Premier League game on 1.04 Expected Goals per game, per Understat. Since van Dijk’s debut for the club, those numbers have been slashed to 0.92 goals per game and 0.87 xGA per game.

Van Dijk isn’t the only factor. Consistency at the goalkeeper position has helped. So has the midfield. And Andy Robertson continues to be a revelation at left back. All of those improvements tip the balance toward Liverpool, and toward an attack that could have two field days with what is, xG-wise, just the sixth-best defense in Serie A.

7. Mo Salah against his former club

Salah will lead that attack. Less than 12 months ago, of course, he was leading Roma’s.

But Salah has been a different player since returning to England. He scored 29 goals in two full seasons in Serie A. He’s scored 31 in less than one in the Premier League. He is setting records and winning awards.

He’s evolved from a proper winger at Roma into a menacing wide forward at Anfield. Salah had been improving as is, jumping from 0.31 xG per 90 in 2015-16 to 0.48 xG per 90 in 2016-17 in Serie A, per Understat. But his move to Liverpool, and nearly seamless transition into Jurgen Klopp’s fluid front three, has helped propel him to superstardom. He’s up to a remarkable 0.77 xG per 90 this season. He’s improved as a finisher, too. He scores against opponents inferior and superior, in transition and against bus-parkers. He does it all. And if your life depended on selecting one player to score in the semifinals, your pick would have to be Salah, right?

OK, maybe not …

8. Cristiano Ronaldo’s remarkable run

Lost in the chaos of Real Madrid’s late winner against Juventus was the fact that Cristiano Ronaldo extended his Champions League scoring streak to a remarkable 11 – ELEVEN! – games. The run dates back to his double in last year’s final. It’s comprised 17 goals in all.

Oh, and Ronaldo is currently riding a separate 12-game streak in all competitions. He’s scored 22 – TWENTY-TWO! – goals in his past eight La Liga matches, the two Champions League legs against PSG and the two against Juventus. Simply incredible.

9. James Rodriguez against his … current club?

James Rodriguez is technically still on loan from Real Madrid at Bayern Munich. He’ll be purchased permanently soon enough. But the narrative cycle will still lap this one up – and with good reason.

James, relegated to second-choice at Real Madrid, endured a rough start to his Bayern career after his summer 2017 move to Germany. He was in and out of the team, and mostly out of form. But since the turn of the calendar year, he’s scored four goals and assisted on eight. He isn’t quite back to his playmaking best, but he’s getting close. And you can bet he’d love to add to his tally against his former – er, current? Parent? – club.

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Henry Bushnell covers global soccer, and occasionally other ball games, for Yahoo Sports. Have a tip? Question? Comment? Email him at henrydbushnell@gmail.com or follow him on Twitter @HenryBushnell.

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