Across 18 games in June, as spring turned to summer in Washington and the Nationals bobbed on the edge of contention, Kyle Schwarber used 70 seconds, give or take, to change just about everything.

Modern baseball is often derided for being a slow game short on action. And often its critics have a point. But try telling that to fans who watched those 70 seconds — the total time Schwarber’s 16 recent homers flew before finding an empty seat, a waiting hand or the third deck at Nationals Park, once the ball dropped from the sky like a bird that had lost its wings. Try telling the Nationals, the team that was desperate for a lift — any lift at all — and was jolted by a 28-year-old who joined Barry Bonds, Mark McGwire and Frank Howard, among others, in the small circle of historic power surges.

Or try telling Schwarber, who was released by the Chicago Cubs in December, struggled through his first two months in Washington and now will never be looked at the same here. That’s what can happen in 70 seconds that are woven through a 162-game season. That’s why Schwarber believes.

“It’s physically impossible to keep hitting a homer every time you get a hit,” Schwarber said during an interview in Miami late last month. “It’s going to come to an end. But I’m not surprised.”

If the season were plotted on a line graph, the Nationals’ success and Schwarber’s numbers would overlap, maybe exactly, making it hard to separate the two. Before June 12, when the team was 25-34, Schwarber had nine home runs in 215 plate appearances and was one reason the offense was underperforming. But since that date, when Manager Dave Martinez moved Schwarber to the leadoff spot, the left fielder has 16 homers in 86 plate appearances entering Friday’s game, bending expectations for each pitch. The Nationals’ record in that stretch was 15-5.

Schwarber did meet a pothole Friday against the Los Angeles Dodgers when, after a single, he grabbed the back of his right leg and left the game. The Nationals later said he suffered a hamstring injury.

But no matter the diagnosis, his exit stung harder because a Miami Marlins announcer had compared him to Babe Ruth in June. One teammate called his hot streak a “joke.” Schwarber is the third player to hit 16 homers in 18 games. That took him from middling to an all-star candidate, from a possible one-off experiment for the Nationals to a player they could keep for the longer term. For Washington, though, it is perhaps most important that he made a promise and kept it.

On June 13, on the doorstep of turning three weeks into his personal batting practice, when the Nationals were still stuck in last place, Schwarber asked fans to “stick with us.” And he gave them 16 reasons to do so.

“I’m a believer,” Schwarber said that afternoon in Miami, more than once, as his bat was making others feel that, too. He stared at the field, arched his eyebrows and smiled a bit. And a few hours later, in his second at-bat of the game, he blasted a homer to the stadium’s fifth-highest row.

‘He did it again’

In his 16 seasons as the Nationals’ play-by-play man and in the thousands of major league games he has called since 1984, Bob Carpenter has seen that a sport built on failure is also a shrine to randomness. Only twice, then, has a player made him feel as if there was a good chance that, in this very moment, the ball could leave the yard.

“This thing takes me back to ’98,” Carpenter said, nodding to the summer he spent chronicling McGwire’s 70-homer season with the St. Louis Cardinals. “Because every time he came up to the plate, you didn’t expect him to hit a home run, but you thought he might. That was the feeling in St. Louis at the time, that for every one of McGwire’s at-bats there was a buzz in the ballpark, nobody was in line at the concession stands, nobody was in the bathroom, nobody wanted to miss it, and I think Kyle has captured that over the last couple of weeks.

“It is very rare to make someone feel like a specific something might happen on a baseball field.”

But Fred Nori should have known, really, because he watched Schwarber launch homers when few others were. Nori, a longtime college baseball coach, counted Schwarber as one of the more athletic kids in Middletown, Ohio, an undersized linebacker with Division I scholarship offers, a catcher with a big swing. He was there when Indiana University recruited Schwarber and he smacked three shots in one game. He was there on the field, hitting grounder after grounder, helping Schwarber learn the outfield so the Hoosiers’ coaching staff could never bench him.

Nori, a Middletown native who trained Schwarber, was one of the early believers. And still, upon glancing at the TV in June, seeing Schwarber pull a towering homer to right, Nori figured it was a replay. It had to be.

“No,” Nori recalled his grandson saying. “He did it again.”

“No way,” Nori answered.

“Yeah,” his grandson said. “He really did it again.”

‘Look at him now’

So if the belief was there before this, before Schwarber flipped a season on its head, where did it begin?

Does it begin in that fifth-grade journal, when the son of a nurse and police chief, the youngest of four with three older sisters, wrote “major league baseball player” as his dream? Does it begin that day at Indiana, when Schwarber told his head coach, Tracy Smith, where each homer would land as his bat ripped through the zone? Or does it begin on Cape Cod, Mass., in the championship game for the famed summer league, when Schwarber had three strikeouts and an error before blasting two homers to win the whole thing?

“Tell that kid he can’t do something and then duck,” Greg Schwarber, his father, said when asked this very question. “That’s how I see it, at least, because there have been times when he was undersized, told he couldn’t play catcher or the outfield, make it to the next level, whatever it was. And look at him now.”

Predictably, Schwarber doesn’t have his own explanation. He knows his home run pace will slow. He laughs at how, despite the two decades of practice, hundreds of days in the batting cage, all those hours spent analyzing the grainiest details on video, he still controls only the split second between starting his swing and ending it.

From there, he says, the rest is dictated by the wind, by geometry and physics, by whether a hit can clear a specific wall in a specific park at that specific moment. He can’t expect each factor to line up, even when everyone else does.