Ryan Zimmerman worked the count full until the scenario that had played out in every kid’s backyard surfaced: full count, two outs, bases loaded, bottom of the ninth, tie game. And the third baseman delivered with his eighth career walk-off home run. (Greg Fiume/Getty Images)

Ryan Zimmerman walked from the Nationals Park on-deck circle Friday night and into the dream in every kid’s backyard: Tie game, full count, two outs, bases loaded, bottom of the ninth inning. A long, wild game had spilled past midnight and led to this. Zimmerman stared out to the mound at Philadelphia Phillies closer Ryan Madson.

“The pressure’s on him, man,” Zimmerman said. “It’s not on me.”

Zimmerman had stepped into a fantasy and responded with nonchalance, the way he treats most every moment on a baseball diamond. He completed the Washington Nationals’ stunning, 8-4 victory with a two-out, full-count grand slam to left field, capping the rally Jayson Werth started with a memorable, 11-pitch at-bat against his former team, whom the Nationals have now beaten four times in five meetings.

The eighth walk-off home run of Zimmerman’s career lifted the Nationals to third place in the National League East, and it validated his place as a hitter who pairs poise and power like few others. Zimmerman has the more game-ending homers than any other major leaguer since he made his debut in September 2005.

“He’s one of those great players who’s totally in control in tough situations,” Manager Davey Johnson said. “He’s very calm. The rest of us get a little excited, but he doesn’t.”

Once he crossed the home plate, his Nationals teammates mobbed him. As he conducted a television interview in front of their dugout, Danny Espinosa smeared a whipped cream pie in Zimmerman’s face, and Michael Morse and Werth dumped a Gatorade bucket over his head.

“The Gatorade surprised me,” Zimmerman said. “That was a cold one.”

The walk-off home runs all the feel same, Zimmerman said, even if Friday’s capped a game not quite like any he had ever played. His laser of a run home run landed at 12:25 a.m., rain having delayed the game just five minutes after it began for 2 hours 22 minutes. Livan Hernandez pitched four innings — and threw countless warm-up pitches because of the delay. Tom Gorzelanny led the Nationals’ bullpen, which produced five scoreless innings while allowing just one hit.

The Nationals came to life, though, in the ninth. Werth had never faced Madson, a former teammate, not even in spring training drills. Madson threw him an 0-1 changeup, his best pitch, and Werth flailed so violently he fell to one knee.

Down 0-2, Werth simplified his approach. “Just try to relax and see the ball,” he said. He would be mindful of that changeup, but he also knew he had to be alert for Madson’s powerful fastball, even if it meant defensive swings. Werth fouled five pitches in between taking three balls, tipping pitches back to the net until he found one he could hit. Finally, with the count 3-2, Werth looked for a fastball, and he lined a 95-mph heater into left field.

“You can’t say enough about that at-bat,” Zimmerman said.

Espinosa followed by flaring a single to left-center. Jonny Gomes grounded a single to left that scored Werth, and an impossibility had become possible — the Nationals, down one with two runners on base and no outs, had a chance to tie the game, if not win.

Ramos laid down a bunt, advancing the runners and, as Johnson surely considered, taking the double play out of play. Madson intentionally walked pinch hitter Jesus Flores, loading the bases. Ian Desmond blooped a single to center with two strikes, tying the game at four.

Rick Ankiel struck out. But that only brought Zimmerman to the plate.

Though Zimmerman had gone 8 for 22 against Madson in his career, he walked to the plate thinking he was “0 for whatever against,” he said. “I’m supposed to get out.” He may have been lying to himself, trying to stay calm.

“The way I’ve always been taught is, the pressure is on the pitcher,” Zimmerman said. “Obviously, I want to get a hit as much as anyone else. But if you kind of put it into that mindset, it puts the pressure on him, keeps you calm. The key thing is to try and not do too much.”

Madson threw balls and Zimmerman smoked fastballs foul until a changeup in the dirt ran the count full. “A 3-2 pitch, bases loaded, it’s pretty hard to throw something other than fastball,” Zimmerman said. Madson threw one, inside, 92 miles per hour.

Zimmerman turned and crushed it down the left-field line. Immediately, what remained of the 37,841 in attendance knew the Nationals had won. The only question was how good of a story they would get to tell. When the ball crept into the first row, they had a whopper.

Zimmerman had his second career walk-off grand slam — the first had also come past midnight, in Florida on May 13, 2007 at 1:42 a.m. The best feeling from all his walk-offs remains the same.

“It’s the ultimate thing when you round third,” Zimmerman said. “Your teammates are waiting there.”

Zimmerman’s home run also stood as his third in three days, another sign that he has returned to full health — and to his stature as one of the game’s elite players — following abdominal surgery in May. In August, Zimmermann is hitting .371/.435/.661. Zimmerman has also solidified his new throwing motion, and on Friday he made two sensational plays at third base.

“He’s wakes up every morning and he’s good,” Werth said. “That’s all you need to know.”

The Nationals mobbed Zimmerman after he reached the plate, then gave him the pie-and-Gatorade treatment. In the clubhouse afterward, reporters gathered by the corner inhabited by Werth and Zimmerman, wondering who they should talk to first.

“Do him first,” Zimmerman said. “He got the hit to start it.”

“Yeah,” Werth said. “But he finished them off.”