How the 2019 World Series is a postseason battle unlike anything we've seen before

Heading into Game 7 with it all on the line, one thing — and one thing only — is clear about this World Series: expect the improbable.

It began with the sheer improbability of the Washington Nationals, who had never won a playoff series, coming from behind to win the infamously-volatile wild card game. It continued when they went on to stave off elimination against the Los Angeles Dodgers twice in the NLDS, in games four and five.

It went further as the Nationals swept the St. Louis Cardinals in the NLCS, and then things began to get inconceivable for baseball come the World Series.

The Fall Classic began with the Nationals defeating the historically dominant Houston Astros in back-to-back games at Minute Maid Park — where the Astros amassed a .741 winning percentage this year — to open the series. But yet, things somehow got crazier.

The Astros fired back with three straight wins in Washington, threatening to end the Nationals’ season Tuesday night back in Houston. Once again, the improbable took hold.

The Nationals won their fourth straight elimination game in comeback fashion, making them the first team to do so in a single postseason.

The game marked the sixth straight win by the visiting team, another first for the World Series — and for any best-of-seven series in any major league that features them (MLB, NBA and NHL). That, remarkably, is through 1,420 best-of-seven series, according to the Fox Sports broadcast.

Additionally, Tuesday’s comeback was fueled by third baseman Anthony Rendon, who himself did something we’ve only seen once before — and the first time was just days ago. According to The Athletic’s Jayson Stark, no third baseman had ever driven in five runs in a single World Series game through last season; but this year, both Alex Bregman (Saturday) and Rendon have done it.

And of course, Game 7 is already expected to feature another never-before-seen gem. When Max Scherzer and Zack Greinke take the mound Wednesday to start for the Nationals and Astros, respectively, it will be the first time former Cy Young winners face off on the game’s biggest stage.

So, only one question remains: do the Nationals have what it takes to cap this series, fittingly, with the ultimate “first”?

More from Yahoo Sports:

• NFL power rankings: It looks like an AFC cakewalk for Patriots

• MLB bans 2 women who flashed Astros pitcher in World Series

• NCAA considers updating rules on athletes profiting off their images

• Report: Nets officials concerned over Kyrie’s mood swings