On the night of Oct. 12, 2012, General Manager Mike Rizzo stood in the center of the Washington Nationals’ clubhouse, addressing the team he had assembled. Rolled-up sheets of plastic hung above lockers. The scoreboard outside — Cardinals 9, Nationals 7 — had not been switched off. The shock from the Nationals’ Game 5 loss in the National League Division Series formed an open wound. The room had turned funereal.

“Don’t forget how you feel right now,” Rizzo told the players. “Let’s do everything in our power to not feel this way again.”

On Friday afternoon, the Nationals will gather at Nationals Park and march back into the postseason for their first playoff game since the deflation two seasons ago — their first opportunity to erase the way they felt that night. The Nationals have added new, better personnel. The core players remaining have been improved by the experiences not only of their roller coaster foray into the playoffs but also the tribulations of the following season.

The Nationals waltzed into the 2012 playoffs as an ascendant, 98-win team that turned into a favorite overnight, in baseball’s timetable. They suffered the heartbreak of Game 5 — blowing a 6-0 lead after three innings and a 7-5 lead after eight — and the malaise of 2013. They learned lessons. They grew up. They developed a tougher hide than they had in 2012, a layer only experience could give them.

“That year, we were so naive to what winning felt like and what playing in the playoffs felt like, kind of entering into the unknown,” Nationals reliever Craig Stammen said. “The season went so smooth, it was almost like we didn’t have to try. We just won every game. This year, things haven’t been always so smooth. That toughness that we’ve developed because of that has helped this team a lot. This team is a lot more resilient. There’s just a little mental toughness to this team that’s a little better than 2012.”

The Post Sports Live crew debates whether the Nationals will be disappointed with anything less than a World Series title after the end of an incredible regular season. (Post Sports Live/The Washington Post)

The Nationals won 98 games in 2012, two more than this season. Think back and compare rosters, though, and the gulf in talent becomes jarring. Just four players — first baseman Adam LaRoche, shortstop Ian Desmond, right fielder Jayson Werth and No. 2 starter Jordan Zimmermann — hold the same roles they did in 2012. The Nationals have upgraded most every other position.

Gio Gonzalez, the Nationals’ postseason ace in 2012, is now their fourth starter. Ross Detwiler provided their best pitching performance in the 2012 NLDS; now he’s a spare part in the bullpen. Danny Espinosa started at second base then. Now he will come off the bench for defense and pinch-running purposes. Tanner Roark posted a 2.85 ERA in 1982 / 3 innings, and he will be relegated to bullpen duty.

Anthony Rendon, one of the best players in the National League this season, arrived from the minor leagues and made it possible for Ryan Zimmerman — the most accomplished player in team history — to come off the bench as his torn hamstring heals. Doug Fister has replaced Edwin Jackson. And as Stammen said, “We got the big horse”: Stephen Strasburg has filled the void his innings limit left in 2012.

“We’ve got more depth. We’re a deeper team. We’re a better team,” Werth said. “We’re more experienced. We’re going to have Stephen Strasburg versus not having Stephen Strasburg. I think we’re more well rounded. We were pretty raw in 2012. We’re a little bit more polished now.”

The 2012 Nationals surprised even their own front office by crashing the playoffs. The 2014 version has been manufactured for them. When Rizzo acquired Fister, Asdrubal Cabrera and lefty reliever Matt Thornton, their experience was “very important as far as roster construction,” he said, because of “where we’re at at this time with this team.”

The Nationals are more talented, and they are more prepared. In 2012, five Nationals had previous experience in the postseason. Zimmermann remembers Werth telling him, “It’s going to be the craziest experience you’re ever going to have.” He still had no idea how he would feel until he climbed the Busch Stadium mound, gazed around and saw 45,000 fans screaming and waving towels.

“We were basically going in blind,” Zimmermann said. “We had no clue what to expect, how rowdy it was going to be.”

The Post Sports Live crew predicts which unsung hero from the Nationals roster is most likely to have a breakout performance in the postseason. (Post Sports Live/The Washington Post)

This year, 19 Nationals will have appeared in a playoff series. Before the 2012 NLDS, Zimmerman called experience “overrated.” He admits now he undervalued it, a notion his teammates can relate to. Stammen said he felt a different physical reaction when he entered the game. Zimmermann said he was too “amped up,” that he tried to match the crowd’s intensity.

“Having a comfort level with the pressures of those situations is a big deal,” reliever Tyler Clippard said. “It’s almost like making your debut. You’ve played hundreds of games in the minor leagues, and then you go to the big leagues and things are different. You feel different. You’re nervous. There are more people in the stands. The crowd is louder. If you’ve never experienced them before, it takes a little while to get used to. Since we’ve been there before, we know what to expect.”

Closer Drew Storen, who blew the save in Game 5, said the Nationals learned not to try to do more than they are capable. They didn’t trust the same routine that got them to 98 wins. This season, he said, “if we just play our way, we’ll be fine.” The experience, they know, does not mean winning will be easier. It means they know how hard it will be.

“That’s what we learned the last time: Nothing is easy,” Zimmerman said. “Every out is hard. Every strike is hard. Everything is so magnified. Every play is huge. When you’re in the game, you don’t really think about it. After the game, you’re like, ‘That was exhausting.’ It’s a fun exhausting. Mentally, physically, every game is do-or-die. I think maybe the biggest thing we learned is what to expect on that level — not so much the physical part but just the toll it takes on you to compete in that situation for nine innings.”

The Nationals also learned from their 2013 season, a debacle for the first four months. They collapsed under the weight of expectations as a lack of depth was exposed. Their offense wilted against the back of bullpens, and they did not erase a three-run deficit until June. This season, they did it on opening day. They won 14 games they trailed after six innings. The 10-game winning streak they used to take control of the National League East included five walk-off victories.

“In ’12, we kind of got by on talent,” Werth said. “This team has an identity.”

Said Rizzo: “There’s a calmness to it. I think guys are more prepared for the big stage. Guys were just more focused and able to absorb the moment better.”