This is it: There's one game to go before the Champions League final. Who will advance to meet on June 1 in Madrid? Do Liverpool have a miracle in them vs. Lionel Messi and Barcelona? Will Ajax or Tottenham advance?

Here's everything you need to know, from the superheroes and the sidekicks who can decide the ties to the keys for victory.

Liverpool vs. Barcelona

FIRST-LEG SCORE: Barcelona 3, Liverpool 0
WHEN: Tuesday, May 7, 3 p.m. ET / 7 p.m. BST

WHAT WE LEARNED FROM THE FIRST LEG: You pretty much dominate your opponent for long stretches, but if Messi comes to life, there's little you can do. Barcelona's win wasn't quite smash-and-grab, but there certainly weren't three goals between the two sides. Liverpool's movement and intensity created all sorts of problems for Barca, and with better finishing from the Reds, this would have been closer.

WHAT CAN WE EXPECT FROM THE RETURN LEG: Barcelona coach Ernesto Valverde gave almost every likely starter the day off against Celta Vigo on Saturday, which means his team will be well-rested. Expect them to try to keep possession in an effort to frustrate Liverpool. Roberto Firmino's absence is a big blow for Liverpool in this sort of game, as is -- obviously -- that of Mohamed Salah, who was ruled out on Monday following the blow to the head he received Saturday. Still, the game plan will be simple: channel the Anfield roar and get right in Barcelona's grills from the first minute. They have nothing to lose.

-- The biggest week for Liverpool in decades
-- Liverpool made Messi angry and paid the price

WHAT LIVERPOOL HAVE TO DO TO REACH THE FINAL: Win by four goals or make it 3-0 and then hope to break through in extra time or on penalties. It's obviously a tough-to-impossible proposition as Barcelona have given up as many as three goals just once this season. If they can rattle Barca early, establish the press, deny possession and force the visitors to hit long balls over the top to get out of their own half then maybe, just maybe, they have a shot. But they'll also need to be more clinical than at the Camp Nou and hope that Messi slumbers throughout the game. And you'd feel much better about their chances if Firmino and Salah were available.

WHAT BARCELONA HAVE TO DO TO REACH THE FINAL: An away goal pretty much guarantees passage since it would count double and would mean Liverpool would need to score five goals. The last time anybody put five past Barcelona was way back in 2003. Keep possession, pick your spots, force Liverpool to foul and wait for the goal-scoring opportunity. Pretty simple, really.

BATTLE TO WATCH: Luis Suarez vs. Virgil Van Dijk. Liverpool need to score and score plenty, which suggests they'll press high and hard, meaning the big Dutchman will be in plenty of open-field, one-on-one situations with Suarez. It won't just be about ensuring he doesn't beat you; it will be about recovering the ball quickly and recycling it forward so Liverpool can continue to keep the pressure on.

WILD CARD/STORYBOOK SCENARIO: Well, it wouldn't be that "storybook." A year ago, Barcelona won their quarterfinal first leg against Roma at the Camp Nou by three goals, a scoreline that flattered them much like this season. And then, in the return leg, Roma -- with current Liverpool keeper Allisson between the posts -- beat them three-nil, knocking them out. Roma exploited set pieces, pressed hard and played a very high line, daring Barca's forwards to beat them for pace, which Messi and Suarez could not do. Can lightning strike twice?

FINAL PREDICTION: Liverpool win 2-1 on the night, but Barcelona advance 4-2 on aggregate. It's too much of a mountain to climb without two of their world-class front three.

Ajax vs. Tottenham

FIRST-LEG SCORE: Ajax 1, Tottenham 0
WHEN: Wednesday, May 8, 3 p.m. ET / 7 p.m. BST

WHAT WE LEARNED FROM THE FIRST LEG: Ajax battered Tottenham for 45 minutes in which they scored once but could have had more, before being pushed back after the break (yet still hitting the post). The Dutch side showed both confidence and maturity, counterattacking well in the second half. Injuries, fatigue and absences finally caught up with Tottenham and they showed little creativity and incisiveness.

-- Spurs have hope heading to Ajax
-- Inside the Ajax "dream factory"

WHAT CAN WE EXPECT FROM THE RETURN LEG: Injuries in midfield forced Mauricio Pochettino to play a back three, but the decision boomeranged badly against a "false nine" center/forward like Dusan Tadic. It also ceded control of the middle of the park to the opposition. Expect a more disruptive Spurs midfield, bolstered by the return from the start of Moussa Sissoko and focused on releasing the returning Son Heung-min into space. Ajax will try to impose their passing and movement on the game, knowing it's the best way to keep Spurs off balance.

WHAT AJAX HAVE TO DO TO REACH THE FINAL: Because of the away goals rule, Tottenham have to score at least twice regardless of whether or not Ajax get on the score sheet. Were this a different team, you'd expect them to sit and look for the counter. Ajax tend not to do that, especially at home, and while you don't want them to ditch the approach that got them this far in the first place, you don't want to leave your central defenders isolated against Son, either. It's the "maturity" that manager Erik ten Hag spoke about.

WHAT TOTTENHAM HAVE TO DO TO REACH THE FINAL: Forget about what came before. Yes, they've lost five of their past six games in all competitions but none of that matters: they're 90 minutes away from a European Cup final. Banishing the "flaky Spurs" trope would be a huge psychological win for Pochettino. All they have to do is score a goal and it's like hitting the "reset" button. The fact that Sissoko and Son will be playing from the first minute is a big boost; make it count.

BATTLE TO WATCH: Moussa Sissoko vs. Frenkie De Jong. Sissoko's physicality and workrate was missed in the first half of the first leg and his presence can relieve Christian Eriksen and Dele Alli of some defensive duties, freeing them up to create. But he also needs to stop de Jong, Ajax's metronome of a two-way midfielder.

WILD CARD/STORYBOOK SCENARIO: Klaas-Jan Huntelaar is 35. Fernando Llorente is 34. Neither striker is expected to start but both could offer something entirely different off the bench and in dead-ball situations should the game warrant it.

FINAL PREDICTION: 1-1, Ajax to advance 2-1 on aggregate. So much depends on Tottenham's state of mind here and right now they seem frazzled, as evidenced by the two red cards picked up over the weekend. (It could have been three if the referee had been stricter with Eric Dier.) Ajax, on the other hand, seem unfazed no matter who the opponent or what the situation.