TELANDER: Once-sleepy Harper, Zimmerman turn tide in decisive 8th

WASHINGTON — We’ve said this before: Baseball is a game of mundane stretches dotted with moments of opportunity.

In other words, stuff can happen really fast.

That was the story Saturday in the Nationals’ 6-3 win over the Cubs to even the National League Division Series at one game apiece.

The Cubs had this game. It was in the bag. No question about it. They had a 3-1 lead after the seventh inning, the Nationals had but two hits and all the Cubs had to do was hang on to leave town up two games to none.

The Nationals and their fans react after seeing Bryce Harper hit a tying, two-run homer off Cubs relief pitcher Carl Edwards Jr. in the eight inning Saturday. | Pablo Martinez Monsivais/AP

Then somebody took his cleated shoe off the Nationals’ sweaty neck and — just as quick as that monstrous home run from Bryce Harper — the game was yanked from the Cubs.

Indeed, the fear now has to be that the shocking eighth inning is indicative of a once-cocky Cubs team folding in on itself while a once-uncertain Nationals team abruptly feels superb.

Don’t blame any of this on Cubs starting pitching. Kyle Hendricks threw seven scoreless innings in the 3-0 win Friday. Jon Lester gave up one run in six innings Saturday. He left with that 3-1 lead, and you’ll forgive him if he might be as shocked with the Cubs’ bullpen as anybody.

Until that disastrous eighth inning, you could almost see the blue-on-white ‘‘W’’ flags blowing in the Chicago breeze, with the Cubs returning home for the game Monday at Wrigley Field needing to win only one of three.

Now it’s even. And as Harper said, ‘‘I think the train’s coming.’’

That would be the Nationals’ offensive train, the one that roared all season long and raced down the tracks in the eighth inning so fast that the Cubs looked like pumpkins splattered to mush.

First came a pinch-hit single by Adam Lind, he of the fully bleached blond hair. No problem, right? Because the next batter, Trea Turner, struck out, bringing up Harper, who had been out for almost a third of the season with a knee injury and had but one single in the series.

He already had struck out and grounded out twice to shortstop Addison Russell. His stick was in the shop for repairs and likely would be for the duration.

Oops.

Cubs pitcher Carl Edwards, Jr. hung a curveball that Harper yanked so mightily to the right-field upper deck that folks at first weren’t sure the ball had stayed in Nationals Park. If the same monstrosity had been jacked to left, it might have rolled all the way to the Capitol peeking its lit-up edifice over the GEICO lizard sign behind the left-field wall.

Suddenly, the game was tied 3-3, and the Cubs’ momentum was destroyed.

‘‘I could have made the wrong pitch to anybody,’’ said Edwards, meaning there wasn’t that much special about Harper.

We beg to differ. Harper is like an electric switchboard to a toaster oven. He goes, the Nats go.

Edwards walked Anthony Rendon and was pulled for Mike Montgomery.

Ka-blooey! Montgomery swiftly gave up a single to Daniel Murphy and then a homer to Ryan Zimmerman. That was it.

One swing from Harper turned the tide. That compact, swift, left-handed swing ‘‘can wake up the team,’’ Nationals manager Dusty Baker said. ‘‘It woke up the fans.’’

You never want to let a foe rub the sleep from his eyes. Now the Nationals have ace Max Scherzer supposedly ready for Monday, and Lester’s gem was wasted.

Lester’s postseason ERA is 1.25. But Edwards’ is 20.25, and Montgomery’s is 27.00.

‘‘You kind of figured they’re due at some point,’’ the Cubs’ Kris Bryant said of the Nats’ offense. ‘‘You just don’t want it to happen all at once.’’

But it sure did.

Follow me on Twitter @ricktelander.

Email: rtelander@suntimes.com