(Brian Garfinkel/Getty Images)

The first major league postseason game in Washington since the 1933 World Series doubles as the Nationals’ most important game since baseball returned. If the Nationals lose today, they will put their season in the hands of Ross Detwiler, the starter who effectively replaced Stephen Strasburg, and the result would unleash all that entails. If they win, they get two cracks at the Cardinals, at home, to advance to NLCS.

The stakes are high, and they will hand the ball to Edwin Jackson, the $11 million free agent the Nationals signed, in part, for his postseason experience. He will face the team with which he won the 2011 World Series. “It’s personal for him,” one Nationals official said pregame, in order to indicate his confidence in Jackson. They think he has the stuff, and the demeanor, to pitch big today.

“If E.J. gives up a run, he’ll come in and say, ‘Hey, that’s all they get,’ ” Detwiler said. “He’ll pump up our hitters and say, ‘Hey, I’m going to go throw up some zeros.’ ”

Jackson unraveled the last time he faced this Cardinals lineup, recording four outs and allowing nine runs at Busch Stadium. But in his one start against the Cardinals this year at Nationals Park, Jackson allowed no earned runs in eight innings.

Here today, the bunting is hung from the facades of the decks (but missing, oddly, in some places.) The home dugout has “October Natitude” painted on top. The Nationals will wear their usual white home uniforms, while most of their fans have followed the team’s directive to wear red.

Even an hour before the game, the place is buzzing. The sun is out, puffy white clouds are overhead, the air is crisp and it feels like an event. Frank Robinson is here to throw out the first pitch. The Nationals desperately need a win against the the defending world champions. This is the good stuff. Get ready for the biggest baseball game in the nation’s capital in 80 years.