Catcher Matt Wieters bats against the Tigers in the in Detroit in a game last September. (Paul Sancya/AP)

The night before Matt Wieters came to Baltimore, the Orioles and the Tigers drew a tea-party-sized crowd of 11,937 to Camden Yards. The next night, the same two teams played again. The only material difference: Wieters replaced Gregg Zaun as the Orioles’ catcher in the lineup. And 42,704 O’s fans, desperate for a franchise foundation, packed the place.

Wieters’s career in Baltimore might not have developed into its MVP promise, and his draw at the box office was short-lived. But he was an essential part of the core that turned a decade-and-a-half of frustration — a period when the club seemed downright wayward — into an annual run at the postseason. Adam Jones, Chris Davis, Manny Machado, Chris Tillman — and Wieters.

And now that piece of the Orioles’ core, drafted and developed and nurtured by the franchise at the northern end of the Baltimore-Washington Parkway, is signing with . . . the Nationals.

There is a baseball element to this transaction, to be sure, and we’ll get to it. But there’s also a fabric-of-the-franchises aspect, too. Whether the Nationals and the Orioles have developed a scratch-and-claw rivalry that captures the hearts and minds of fans, at the highest level of the two clubs, there is real rancor. Don’t doubt it.

The ownership groups of Peter Angelos in Baltimore and the Lerner family in Washington are embroiled in a legal fight, one in which the Nationals believe the Orioles are denying them a fair share of revenue generated by the Mid-Atlantic Sports Network — an argument they have said, in court documents, infringes on their ability to build a club.

So there is more than a little symbolism here. Wieters’s time in Baltimore included four all-star appearances and two Gold Glove awards, but it was over. Signing with the Nationals — for a year at $10.5 million, with a player option to stick around in 2018 for another $10.5 million, according to The Post’s reporting — guarantees annual matchups with his old club, his old ownership group.

This isn’t quite Ryan Zimmerman ending up with the Orioles. But it’s not nothing. There had to be some fantasizing in the Lerner offices in Rockville on Tuesday, not to mention at Nationals Park, of a moment this coming spring when Wieters might step to the plate and deliver the blow for Washington to beat Baltimore — for the Lerners to beat Angelos, even for a night.

In a way, Wieters’s arrival in Washington serves as a reminder of how good we have it now — and how bad we had it then. In becoming the most prominent player to wear both the Orioles and Nationals uniforms, Wieters overtakes such luminaries as Winston Abreu, Daniel Cabrera, Bernie Castro, Alex Cintron, Luis Matos, Keith Osik and Corey Patterson.

Truthfully, there may be no better way to gauge how bad Beltway baseball was from 2005 to 2011 than to peruse the list of players they shared. (Cesar Izturis? A broken-down Nick Johnson? Luis Ayala and Michael Morse were fine, sure, but John Halama and Jerry Hairston Jr. and an about-to-retire Jeffrey Hammonds? Yikes.) Only the Royals and Pirates lost more games during that seven-season stretch, so it makes sense that the players who drifted between the two franchises were largely irrelevant.

Wieters is the only player since baseball returned to Washington whose hat-change really matters. He is a good player being added to a good team. However the Nationals resolve their sudden glut at catcher — with veterans Derek Norris and Jose Lobaton joining prospect Pedro Severino at camp — Wieters enhances the bottom part of the lineup.

What’s wrong with a 6-7-8-9 that goes right-handed-hitting Jayson Werth, the switch-hitting Wieters, right-handed Zimmerman and then the pitcher? If Zimmerman rebounds from one of the worst offensive seasons in the game last year, fine, move him up. And if Norris, a former all-star who became a .186 hitter a year ago, or Lobaton plays when Wieters needs a day off — which he will, given his Tommy John surgery in 2014 and the fact that the Orioles started someone else behind the plate 51 times last year — the catcher can hit eighth.

Whatever. If Wieters is healthy, the lineup is deeper than it was a day ago, and the Nats, in another season in which they intend to win, are closer to replacing the pop the departed Wilson Ramos represented. If Wieters is gone after this season, all the better: It will mean he produced over the coming season and thought re-entering free agency made more sense. The Nats get a contribution to a run at a fourth division title in six seasons — and are on the hook for nothing more.

And if some of Wieters’s contributions come against Baltimore, all the better for Washington, and for the Lerners. Care to dismiss the relationship between the two ownership groups as having nothing to do with the on-field product? Consider that the last trade between the two franchises came in 2001, when one wasn’t even in its current city. (If you had the Montreal Expos sending Tim Raines to the Orioles, for whom he played four games, in October 2001, stop by my desk for your prize.)

Since the Expos relocated to Washington, the Nats’ two general managers, Jim Bowden and Mike Rizzo, have completed trades with every other franchise in baseball. That is not a coincidence. An example: A few years ago, when the rebuilding Nationals were looking for pitching prospects on which they might buy low, they targeted struggling Orioles right-hander Jake Arrieta. It was a non-starter for ownership. The Cubs pounced. All Arrieta has done since is win a Cy Young Award and a World Series ring.

So the relationship matters. And it’ll matter, too, later this summer, when the best late-inning reliever who could be on the market just might be Orioles closer Zach Britton.

Wait, what’s the Nationals’ most obvious hole this spring? Oh, yeah. Closer.

Look elsewhere.

When the Nats open the season April 3 against Miami, 40,000-plus won’t show up to see Wieters. But he does represent something beyond what he brings, baseball-wise. He provides a reason to circle May 8, when the Nats travel to Camden Yards, and Wieters, for the first time in his life, heads to the visitors’ clubhouse. What he does that night will matter a little more — even if it’s to the owners, and not so much the fans.