Fifteen years ago, Ryan Zimmerman celebrated his 21st birthday by going 2 for 4 with a double and a run for the fledgling Washington Nationals in a victory in Miami. It was his 17th major league game. Over the next 14 years, 1,672 more would follow.

On Monday, Zimmerman celebrated his 36th birthday just as he had spent each day the past six months: at home with his wife and three young kids. There had been no baseball the day before. There would be no baseball the day after.

“It’s been weird,” Zimmerman said.

Which is a fine summation of the 2020 MLB season. Zimmerman is the Nationals’ career leader in essentially every meaningful offensive category: games, hits, homers, on and on. He entered spring training in 2020 intending to add to those totals. And then the novel coronavirus pandemic hit, and he decided to sit out and stay home — a nod to his newborn son, Henry, who will be 4 months old this week, and his mother, Cheryl, who has multiple sclerosis, as well as to the unknown.

So as baseball’s largest playoff field follows its shortest season, what the heck was it like for a person who knows nothing but baseball to have absolutely none of it?

“To go from playing a game nearly every day and traveling to literally being home — and not just being home, but being home and not being able to really go anywhere or do anything, it’s literally like going from 100 miles per hour to zero,” Zimmerman said by phone late last week. “You’re completely thrown right into that life of family, kids, school, stuff like that. I’m not saying that’s a bad thing. But it was definitely a transition — for everyone.”

Zimmerman — along with pitcher Joe Ross — announced his decision to opt out of the truncated 60-game season at the end of June. After issuing a statement, he didn’t speak publicly about his choice until now — despite some people (looks in mirror) hounding him to articulate what it’s like to watch from the outside something he long had experienced from the inside.

But Zimmerman did not want to draw attention to himself and become the face of the opt-out, which included former teammate Ian Desmond of the Colorado Rockies, Los Angeles Dodgers pitcher David Price and others. And as the virus ripped through the clubhouses of the Miami Marlins and St. Louis Cardinals — putting the season in peril for a couple of weeks — he didn’t want to be seen as saying, “I told you so.”

“I respect the heck out of the guys — on all the teams — who have kind of grinded and played through this and done what they’ve done for the league and for the fans,” Zimmerman said. “Losing an entire year would have been devastating.”

And yet, at 35, that’s exactly what Zimmerman chose to do: lose a year. Even after the strange season of following from afar, his conclusion: He would do it again.

“I think, for me, it was a pretty easy decision,” he said. “But to use a golf term, I was in ‘Position A’ to make the decision. We had just won the World Series. I had been in the big leagues for 15 years. Monetarily, the decision was a no-brainer. Most of the guys, the decision [to play] was based around money or service time, which can put you in a tough spot. You can’t afford to lose a year of service [which brings a player closer to free agency]. . . .

“But for me, not only would I be putting my newborn at risk, but I would have basically said, for the better part of this year, that I wasn’t going to be able to see my mom — and more importantly the kids wouldn’t have been able to see my mom. My mom is fine. There’s no imminent health risk. But a period of time in her life is a lot different than a period of time in our lives. Just the unknowns at the time, all the variables, it was the right decision.”

On Tuesday afternoon, baseball’s postseason begins. On the corresponding Tuesday a year ago, Zimmerman appeared as a pinch hitter in the eighth inning of the National League wild-card game. He fisted a two-out, broken-bat single up the middle off Milwaukee reliever Josh Hader, sustaining the rally that ended with Juan Soto’s bases-loaded single to right that sneaked under the glove of Brewers right fielder Trent Grisham, sending Nationals Park into the kind of delirium it had seen only rarely. Watch that inning again on YouTube, and you’ll have a clear reminder of what will be lost this October: the nail-gnawing, throat-straining, beer-tossing glee that only a packed park can produce.

Those moments are why you do it.

“I miss competing,” Zimmerman said. “I miss the challenge of going out there and maneuvering through a season, where you have times you feel good, times you feel bad. I miss being around the guys — all of that.”

He did not pick up a bat during his opt-out. His relationship with the team was built on occasionally texting some teammates and having the games on in the background as he made dinner or sat with his family on the deck, checking his phone. He worked out, but more for his mental health than to keep his body game-ready.

So the natural question becomes: Did this pandemic-inspired preview of what retirement might look like convince him to actually retire?

“Everyone’s like, ‘You got to see what it’s like to be retired,’ ” he said. “Kind of? I guess? I envision when I retire we’d be taking trips with the family. And we’ve kind of been, I don’t want to say trapped, but we’ve been pretty safe.”

So in the next month or two, he has more to mull. If he is going to try to play a 16th major league season, he’ll have to grab a glove and play catch. He’ll have to get in the cage and take some hacks. He has been a National since before he could legally buy a beer. As a father of three who’s closer to 40 than 30, he believes he can still produce, particularly in a limited role. But he also knows wanting a job doesn’t guarantee him one.

“To sit out a year and expect to just be given a spot, I don’t think that’s how it works,” he said. “You have to prove that you can still play. Taking a year off at age 36 is probably not the best thing to do. But who knows? Some people said maybe taking a year off and working out and getting healthy would maybe make you better.”

For now, he is like the rest of us: helping 6-year-old Mackenzie negotiate remote first grade, preparing 4-year-old Hayden for preschool, helping wife Heather with little Henry in ways that he couldn’t have had he been on the road for work. The opt-out is now over. The virus, eventually, will allow baseball to return to what it had been. The next decision for Ryan Zimmerman: Will he be playing when he’s turning 37, or did the virus prematurely end his career?