Who expected this -- the 107-win, top-seeded Astros, down two games to none in the World Series to the Nationals after losing twice at home with aces Gerrit Cole and Justin Verlander on the mound?

But here we are. The favorites are now the underdog. The Astros have to go on the road for three games in Washington and try to force the Series back to Houston.

If anyone can come back, it's the Astros. But what are the odds?

We can put some numbers to the Astros' chances. FanGraphs' postseason odds – which are powered by the ZiPS projection system -- estimate how likely each team is to win the World Series, and in how many games, based on game-by-game breakdowns of the pitching matchups, offenses and home-field advantage.

Here's how the Astros' comeback chances break down:

Astros win World Series: 25.7%
Nationals win World Series: 74.3%

Astros win in 6: 7.8%
Astros win in 7: 17.9%

Nationals win in 4: 22.7%
Nationals win in 5: 24.2%
Nationals win in 6: 17.2%
Nationals win in 7: 10.2%

After dropping Games 1 and 2 at Minute Maid Park, the Astros are projected with a slightly better than one-in-four chance of winning their second title in three seasons.

Look at it this way: Mets outfielder Michael Conforto (a 2017 All-Star!) hit .257 this year, which means that the chances of him getting a base hit in a given at-bat are the same as the Astros coming back and winning the Series. That doesn’t sound so bad if you’re a Houston fan, right? Conforto gets a lot of hits!

Still, it's kind of amazing to see how much the odds have swung against the Astros over just two days. Per FanGraphs, the Astros entered the World Series with 59.7% championship odds to the Nationals' 40.3%. Houston's chances are now less than half of that.

But here's one testament to how good of a team the Astros have. If the situations were reversed, and Houston was the team up 2-0, the Nationals' chances of a comeback would only be about 13% … about half of where the Astros sit right now.

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So what needs to happen from here on out for the Astros to pull off this Fall Classic comeback? Here's a look at each game for the rest of the Series:

Game 3: HOU@WSH (Friday, 8 p.m. ET)
Starters: Zack Greinke (HOU) vs. Aníbal Sánchez (WSH)
Win probability: 58.3% Astros, 41.7% Nationals

Here's the start of a theme: the Astros are favored in nearly every game. In four of the five potential remaining games, in fact. They're still big underdogs for the World Series overall, because they actually need to win four times; the Nats only need to win twice.

The Astros' edge at the single-game level is thanks to an offense that's been superior over the course of the season (despite the Nats getting to Cole in Game 1 and the fireworks of Game 2) and a pitching rotation that at least evenly matches Washington's counterparts (again, despite the events of Games 1 and 2).

Take Game 3's starting pitching matchup, Greinke vs. Sánchez. Sánchez has been much better this postseason, with a sparkling 0.71 ERA to Greinke's rocky 6.43. But Greinke was a top pitcher all year, finishing the season with a 2.93 ERA to Sánchez's 3.85. Greinke was 54% better than MLB average; Sánchez was 19% better.

Still, those might look like steep odds against the Nats to you, considering how they're clicking on all cylinders. So let's say you think Greinke doesn't give the Astros quite so big an edge over Sánchez -- even a small adjustment to how much you think each starter will impact the runs scored in the game can bring the win probability a lot closer to 50-50.

Game 4: HOU@WSH (Saturday, 8 p.m. ET)
Projected starters: Bullpen game (HOU) vs. Patrick Corbin (WSH)
Win probability: 45.6% Astros, 54.4% Nationals

This is the Nationals' biggest edge. In fact, it's the only remaining game where the projections give Washington the edge over Houston. You've got a very good starter like Corbin, pitching in his home park, as the Nationals' offense gets to face what will likely be a string of Astros relievers plus Jose Urquidy.

And there's a good chance that Corbin is actually an even bigger advantage than those odds suggest. If you think a Corbin-led game is, say, 20% better than an Astros “bullpen game,” the Nats' odds to win Game 4 would jump to over 60%. And a win in Game 4 would be huge for their World Series chances overall, since they'd only need to pull off one win elsewhere.

Game 5: HOU@WSH (Sunday, 8 p.m. ET)
Projected starters: Cole (HOU) vs. Max Scherzer (WSH)
Win probability: 52.2% Astros, 47.8% Nationals

This could change if the matchups do -- what if the Astros fall to 3-0 and feel forced to bring back Cole on short rest in Game 4? But assuming a rematch, Cole and Scherzer are about even ... and "even" means "as good as it gets." If they rematch in the final game in Washington, it should be close to a tossup.

So why the edge for the Astros? They get a slightly bigger boost from offensive firepower than the Nationals do from home-field advantage. But again: maybe you think the Juan Soto and Anthony Rendon-led Nats can slug with the Astros. In that case, Washington would actually become the favorite in Game 5, with winning odds around 55%.

Game 6: WSH@HOU (Tuesday, 8 p.m. ET)
Projected starters: Verlander (HOU) vs. Stephen Strasburg (WSH)
Win probability: 56.1% Astros, 43.9% Nationals

A rematch between Verlander and Strasburg is just like a rematch between Cole and Scherzer. They're both aces, and they might well produce a duel.

But the Astros would be favored more heavily in this rematch than they would for a Cole-Scherzer duel in Game 5, because they'd have forced the Series back to Minute Maid Park. They're usually a powerhouse there. If they get to Houston, and get to run out Verlander again, the Astros can flip the script from Game 2.

Strasburg has been lights-out in the postseason -- not just this year, when he has a 1.93 ERA and a 40-to-2 strikeout-to-walk ratio, but in his career, for which he sits at 1.34 and 64-to-6. But it can be done. Just ask Alex Bregman, who took Strasburg deep in their first World Series matchup. And Verlander can be just as unhittable.

Game 7: WSH@HOU (Wednesday, 8 p.m. ET)
Projected starters: Greinke (HOU) vs. Sánchez (WSH)
Win probability: 63.8% Astros, 36.2% Nationals

This is it. If the Astros can make it all the way to Game 7, they'll have a great shot at winning the Series.

A Greinke-Sánchez redux is, again, the Astros' biggest pitching advantage ... on paper. Their offense would get to mash at Minute Maid, where they've won both winner-take-all games since 2017.

Of course, anything can happen. And maybe the projections are underselling the Nats for a Game 7 -- not just because of how they've been playing, but because if the World Series comes down to one game, Scherzer and Corbin are likely looming in the Washington bullpen.

Say you think Sánchez/Scherzer/Corbin is even with Greinke and Co. Then the Nats' odds climb over 40%. Say you think the Nats' trio is actually better. Then their odds reach 45%. The Astros would still likely be favored going into Game 7, but it's not so hard to imagine the Nats coming through.

The only way to know is to play the game. And what's more exciting than a World Series Game 7?