The grounds crew starts to prepare the field to resume play at Nats Park. (Katherine Frey/The Washington Post)

Around 50 blue-clad fans gathered behind the visitor’s dugout, and another 150 or so clustered behind the Washington Nationals’ side. Both groups cheered every pitch. Players could hear not only hecklers, but also polite, private conversations. When a reliever threw a warmup pitch in the bullpen, the snapping leather echoed throughout Nationals Park.

About 20 minutes before midnight Monday, a D.C. public schools game broke out between two big league teams. The Nationals beat the Los Angeles Dodgers, 4-0, after a 3-hour, 17-minute delay emptied the stadium and transported some of the wealthiest, most famous ballplayers in the world back to American Legion ball.

“You just have to stay focused,” Manager Matt Williams said. “You look at it as an opportunity: We waited around this long. We might as well win it.”

At 1:21 a.m., 6 hours, 16 minutes after first pitch, as Cinco de Mayo parties wound down and chairs went up on bars, the Nationals moved into first place. The Atlanta Braves’ seventh straight loss, the end of which played on the Nationals Park video board, cleared a path for them to lead the National League East for the first time since April 11. All they need now is to hold on for 130 games.

After Jordan Zimmermann fired four scoreless innings, rain truncated his night. (“I don’t remember what happened,” Zimmermann joked afterward.) Five Nationals relievers combined for five scoreless, three-hit, seven-strikeout innings. They tagged in for one inning apiece and saved Williams from using either Craig Stammen or Ross Detwiler, both of whom were available Tuesday in long relief behind starter Blake Treinen, whom the Nationals summoned from Class AAA Syracuse.

Anthony Rendon’s two-run homer in the first inning off Zack Greinke, produced with a how-did-he-do-that swing, provided the only offense the Nationals needed. Danny Espinosa chipped in an insurance two-run shot, his fourth homer this year, in the eighth.

The Nationals’ MVP may have been grounds crew chief John Turnour, whose team enabled the game to restart at 11:43 p.m. Not a soul occupied the second or third deck. The radio play-by-play call reverberated around the barren concourses and onto the field. The out-of-town scoreboard showed Tuesday night’s matchups and start times. If not for the hearty 200 fans who waited out the delay, an observer may have suspected 50 big leaguers sneaked into the park.

“You can hear every word,” Espinosa said. “It’s like a backfield spring training game.”

The Nationals’ bullpen entered with a collective 1.98 ERA. Monday night — Tuesday morning, really — served as its opus. Williams chose Aaron Barrett to restart the game in the top of the fifth. He passed the baton to Jerry Blevins. Drew Storen worked around Matt Kemp’s leadoff double in the seventh. Tyler Clippard handled the eighth. Rafael Soriano pushed his scoreless innings streak to 24 innings in the ninth.

“It’s been fun to watch them,” said Barrett, who was credited with the win. “I’m trying to do my job . . . and let those guys do their job behind me.”

Left fielder Nate McLouth provided Clippard a courageous, painful assist. With one out in the eighth, Dee Gordon sliced a flare down the left field line. McLouth sprinted about 100 feet and slid into the wall in foul ground. He smashed both knees and his wrist, but still held on to the ball. He limped off the field holding his bloodied right index finger. As he walked down the dugout steps, replaced by Kevin Frandsen, every teammate high-fived him.

“That ball looked like it was less than a foot from the wall,” Espinosa said. “For him to lay out right there and make that catch, that’s selfless right there.”

Somehow, McLouth emerged relatively unscathed.

“He’s okay,” Williams said. “Banged his knee pretty good. Pulled his thumb back a little bit. Cut himself open pretty good. No stitches. He should be fine. I think he’ll be a little bit sore, but he’s good.”

In the first inning, the frame the Nationals typically use to dig themselves a deficit, the Nationals drilled Greinke. Denard Span lined a double to left field, which brought Rendon to the plate.

Greinke twirled an 83-mph slider that dived to ankle-height. Rendon flicked his wrists, and the ball zoomed up into the air, toward left-center field. After Rendon made contact, his back knee nearly touched the batter’s box dirt, and his front shoulder dropped to the level of the catcher’s mask. By all appearances, he had been fooled into an awkward hack.

The flight of the baseball told a different a story. Rendon possesses a preternatural ability to club the middle of the ball with the barrel of his bat. Kemp, playing center field, sprinted to his right, like he might catch the ball in the gap. He realized his mistake, turned and headed toward the fence. The ball landed in the second row.

Rendon had hit a slider at his shins into the red seats, which added to the list of feats teammates pass around in the clubhouse. Last week in Houston, Rendon rocketed a curveball over the right field fence. When he returned to the dugout, a teammate asked if he had picked up the opposing pitcher’s tell — he had been tipping his offspeed pitches. Rendon neither needs nor cares for such information. He smiled and replied, “I just hit the ball.”

In the middle of the fourth inning, the persistent rain strengthened. Greinke crouched on the mound as grounds crew members scurried behind him, lugging bags of kitty litter over their shoulders and raking it around the infield dirt.

After Dodgers Manager Don Mattingly conversed with the umpires, they finally called the Dodgers off the field, and the grounds crew pulled the tarp. The crowd cheered when the video board showed the Wizards-Pacers playoff game.

Most of the fans left after the Wizards finished off their Game 1 victory. Those who stayed created a new memory, a game that ended the day after it began.

“The place wasn’t exactly rocking,” Zimmermann said. “It was a game we had to play, and we wanted to win.”