During a series against the St. Louis Cardinals a little more than two weeks ago, Washington Nationals third baseman Ryan Zimmerman reached base, and first baseman Matt Carpenter made an observation that has become painfully clear to Nationals opponents in the second half of the season.

“Literally, everyone at every position can hit a home run,” Carpenter said to Zimmerman. “You don’t see that too often.”

In the first half of the season, the Nationals won because of their stellar pitching and in spite of their meager offense. But in the second half of the season, the offense has exploded, capped by a recent stretch of home run prowess that bordered on the absurd and was previously unseen around here.

Consider the numbers: the Nationals entered Sunday night eighth in the majors with 173 home runs. No team in the National League has sent more balls over the fences in the second half. With every next home run, they set a team record for most hit in a season. From Sept. 4 through Sept. 8, they slammed 20 home runs in five games — last accomplished by the 2006 Atlanta Braves. The Nationals are an in­cred­ible 38-7 in games in which they homer at least twice.

“Because our pitching has been so good we’re almost kind of overlooked offensively,” Zimmerman said.

The Nationals could end up with five players hitting 20 home runs in a season. Think back to the early teams in Washington — such as the 2005 one that finished last in the majors in home runs — and re-read that last line. Adam LaRoche, Ian Desmond and Zimmerman have already eclipsed the 20-home run mark, while Bryce Harper is one away and Danny Espinosa sits at 16 home runs. And that’s without middle-of-the-order slugger Michael Morse, who missed the season’s first 50 games.

“It’s a rare thing,” Manager Davey Johnson said. “Like I said last August, the potential on this ballclub was tremendous. If we just played to our potential, each individual took care of their own little job, we can have a real fun year. I’ve said it before: I don’t think I’ve ever had an infield as talented as this infield.”

Last year, the Nationals managed only 154 homers, tied for 15th in the majors in home runs, and tied for 17th in 2010 with 149.

The biggest reason for the second-half surge is health. The Nationals didn’t have their complete lineup — with the exception of injured catcher Wilson Ramos — until Aug. 17, when Jayson Werth returned from a broken wrist. LaRoche was out most of last season because of a shoulder injury. Zimmerman overcame his shoulder trouble with a cortisone shot on June 24. Desmond recovered from an oblique injury that sapped some of his power.

“We didn’t show a lot of power there for a while,” said LaRoche, the team’s most consistent power hitter all season, who reached 30 home runs on Saturday for the second time in his career. “We just hit a couple month stretch where [we] hit a bunch of homers. It’s just a product of good at-bats, being selective and putting better swings on balls which is putting balls outs. It’s almost like it’s been a little bit contagious.”

But it’s a little more than that. Three of the Nationals’ core power hitters are young and learning. Desmond, 26, is in only his third full season in the majors and learned how to maximize his potential. Espinosa, 25, has hit 37 home runs in his first two full seasons — no small feat — and has improved as an overall hitter this year. Harper, 19, who has as many home runs as his age, has produced a historic power-hitting season for a teenager.

“That’s kind of the scary thing about our team, offensively and pitching and all that, we’re still a relatively young team that still has a lot to learn and a lot to improve on,” Zimmerman said.

The result of a lineup that packs so much power is that opposing pitchers can lose focus. LaRoche said he notices that pitchers can execute better when they’re not concerned about the hitter on deck. When the pitcher worries about the following hitter, it benefits the player in the batter’s box.

“That’s when we end up getting pitches out over the plate, hanging breaking balls,” he said. “So it’s a big difference.”

Johnson’s influence on the team has also had an impact. He prides himself in helping hitters, especially young ones, improve their craft. When he took over as manager last season, he pushed to get rid of an organizational philosophy of hitting the ball to the opposite field. He pushed Morse, Espinosa and Desmond to ignore that and just hit the ball where it was pitched.

“Being such an offensive-minded guy, we don’t bunt as much as we used to,” Zimmerman said. “He would rather just let us hit. So I think us kind of knowing that and having the confidence in us kind of helps us a little bit, too.”

After launching his 23rd home run of the season on Wednesday, Desmond was asked about his continued power this season and how many more he could have hit had he not missed 25 games this season with injury.

His reply: “40 maybe?”