In the three weeks since the Washington Nationals won the World Series — excuse me while I slap myself — the Nationals player who has crossed my mind most often is statistically the least important: Gerardo Parra.

Parra’s impact on the Nats is going to be one of the most vivid memories of my baseball-covering life. From his dugout dancing to his “Baby Shark” walk-ups, Parra was the catalyst that helped an injured, slumping and depressed team discover the freeing power of joy in play and unconditional mutual support.

But I couldn’t figure out how the Nats — as a franchise or as individuals — were going to move on constructively, still loving Parra but recognizing the impossibility of duplicating his almost magical one-time-only impact on their championship.

Parra solved it for them, just by being himself. When he signed Wednesday for a guaranteed $2.5 million with the Yomiuri Giants of Japan, my first reaction was: That’s as good as you can do in a situation that is inherently unfortunate.

Parra loves to play baseball — not just (primarily) cheer for others as the 25th man. He is relatively young — not 33 until next May. If he stayed with the Nats, he would barely play. If he signed with another major league team, he might soon find that he barely played there, too. And feelings might end up hurt.

So he went where he could play — where he could be joyous on the field — and where he also could make (probably) twice the money that he could in the majors as a veteran who, despite all his wonderful clutch moments as a Nat, hit just .234 this past season. Parra could go to Japan, the one serious league, the one destination that made everybody think, “Good for Gerardo. They’ll love him in Tokyo.”

Baby Shark didn’t swim away for money. He had 10 seasons with more than 100 hits in the major leagues and made $42,371,000, plus the generous pension that goes with nine years of major league service time.

Parra left to play more — a lot more. And to make everybody on his new team just a little happier. Maybe some Giants need a hug.

For the Nats and their fans, there would be one better outcome. If we could all freeze time — make it Oct. 30, 2019, forever — then that would fix everything. We could keep chomping for eternity.

And the Nats, hanging by a thread for most of their last 112 regular season games and 17 in October, too, could keep riding their Baby Shark wave in a universe where every home run really did seem worthy of a dance party if they were ever going to get, as they always vaguely put it, “where we want to go.”

But the page turns, damn it.

Fortunately, the championship rings, for a team on which only one player (Hunter Strickland) previously had one, still will be put on fingers next spring. And Gerardo Parra will never buy a drink in D.C. again.

Champions endure change. That’s part of the reason that just seven of the past 50 World Series winners — and none this century — have won again the next year. But 12 of the 50 winners did go back to the next World Series — 24 percent, pretty good odds. Worth the effort!

Now that Parra, who went just 11 for 61 after Aug. 13, is gone, how do those who run the Nats focus on a central baseball reality — as hard as it is, as poor as the odds, a team’s best chance to play in or win another World Series is almost always the next year.

On average, in a 30-team sport, a city is probably only going to have about one World Series-winning parade per generation. And D.C. just had one. But let’s not kid ourselves: All seasons are not created equal. In the next 30 years, I can tell you right now which season I think is the most likely one for the Nats to go to the World Series: It’s 2020.

All the other years in the future get harder and harder to see in the distance. But next year is right in focus, both as opportunity and challenge.

If the Nats can sign their two huge free agents, Stephen Strasburg and Anthony Rendon — which may require (roughly) $400 million for deals that make them both Nats through (roughly) 2025 and 2026 — then improve their worst-in-baseball bullpen, they look like a 95-win (or more) team in 2020 and one of the four or five best teams in the majors. Scary as that is — gee, just one of five — it’s about as good a deal as you ever get.

What if this almost-perfect world is not available?

If they simply keep Strasburg, who loves his teammates — he hasn’t danced with anyone else, has he? — and also certainly seems to feel at home in Washington, then the Nats’ future as a serious contender should remain intact. The Nats should go hard for Rendon. But they must have Strasburg so that their starting rotation of him, Max Scherzer, Patrick Corbin and Aníbal Sánchez can remain intact. Yes, Joe Ross, Austin Voth and Erick Fedde, too. Loaded.

Also, if the Nats get business done with Strasburg (sooner is better), the more likely Rendon will be to say, “Why would I leave that team?”

The Nats have offered Rendon about $215 million for seven years — no one knows how much deferred for how long. But that shows how much, at a minimum, the Nats think they can spend.

With infield prospect Carter Kieboom, 22, presumably ready to take over at either second or third base, the Nats have lots of options in the free agent market to rehabilitate their offense if Rendon should leave.

Nobody is saying that Josh Donaldson (.900 on-base-plus-slugging percentage) or Mike Moustakas (35 homers) are Rendon. Or that going after catcher Yasmani Grandal or first baseman José Abreu (123 RBI) or others would be able to completely compensate for a lack of Tony Two Bags.

But the message of Baby Shark swimming to Tokyo should be clear.

The 2019 Nats can never be duplicated. They already are being frayed around the edges. But 2020 and 2021 are both enormous opportunities to keep their Three Aces — Strasburg, Scherzer and Corbin — together with a first-rate contender around them, including Juan Soto, Trea Turner, Adam Eaton, Kieboom, Victor Robles and To Be Named.

Those Parra-Strasburg hugs are an image that will be long remembered in Washington. Don’t let both halves of it get away.

For more by Thomas Boswell, visit washingtonpost.com/boswell.