No Game Today.

In every pro ballpark that’s what the sign says outside the home plate gate on off days. Those words also greet you and chill you on what feels like the longest off day of all: the 3,000 hours, give or take, until spring training.

The Nationals have no game today. But they could have, and several more, too. They might be playing the Giants now for the National League pennant.

Why aren’t they?

First, let’s look at the big picture and be honest.

The Cardinals won the NL Division Series because they were the better team. Late in the season, the streaky Cards got hot. They doubled the score on the Nats in the playoffs: 32-16. Come on, who deserves to advance? Don’t drive yourself crazy nit-picking all winter. Answer: St. Louis.

The Nats were 10 games better over the whole year and, head to head, ended up 6-6. That doesn’t count. The Cards were better at the right time.

Second, the Nats were hit by big-time pressure in the last few weeks. Everybody reacts differently to pennant race, playoff and, for that matter, World Series pressure. There are stress levels the young Nats haven’t even reached yet. But facing an elimination game and a winner-take-all game is a great education. You don’t know how your heart will beat until you’re there.

Gio Gonzalez looked like a man on a burning deck early in Game 1. In a hairy jam in Game 5, he was less rattled. Though “improving” from four walks to three in a bad inning is a relative term. Bryce Harper was anxious, chasing and 1 for 18 in the first four games before having a triple and a homer. As they say in the pool halls, “you have to pay to learn.”

Postseason isn’t about learning the game. It’s about learning yourself. The Cardinals already read that book. And the schooling showed.

The best compliment to the Nats, both in talent and team temperament, is that they came within one strike of winning back-to-back pressure games against a team that, within 13 days, clubbed them 12-2, 10-4, 12-4 and 8-0.

The experience gap between two teams may never have been greater in the postseason than in this matchup, with the Nationals being the majors’ second-youngest team. Yet the Nats ignored and overcame it. Almost.

And what an “almost.” You may not want to revisit the Game 5 tape. Yadier Molina took a 2-2 slider that missed the low-outside corner by two or three inches. Perhaps he remembered Drew Storen had struck out the previous hitter in the same count on the same pitch in the same spot.

The next hitter, David Freese, checked his swing by one inch.

Or, at most, two inches. Ump Ed Hickox got the appeal right, saving the Cards from elimination. Nice goin’, Ed. How ’bout blowin’ one sometime?

Oh, sorry.

I’d get a photo of that “Freese frame,” but it brings back memories. In ’79, a Post photographer gave me a picture with his caption: “Eddie Murray’s grand slam wins Game 7 of World Series.” In reality, Murray’s blast was caught at the fence. The O’s blew a three-games-to-one Series lead.

Before we say goodbye to Game 5, let’s be blunt about why it was lost. The Cards walked one man; the Nats walked eight. That’ll do it. Gonzalez, Edwin Jackson and Storen, all power arms, nibbled when the proper strategy (they all had sufficient leads) was aggression. The result: seven walks that led directly to five gift runs in a 9-7 loss.