The Washington Nationals - the team everyone thought would dominate baseball - have a huge roster flaw that's killing their offense

The Washington Nationals are in a borderline unimaginable tailspin that's dropped them below .500 with 45 games to go.

The Nationals have dropped six games in a row and are now four-and-a-half games out of the lead for the NL East.

While that's not an insurmountable lead, it's a shocking drop considering many people picked them to win the division and potentially compete in the World Series, too.

While many people have focused on their pitching struggles, with injuries and an ineffective bullpen, their offense has also been a problem, particularly because of one flaw in their roster construction.

As one NL scout told James Wagner of the Washington Post, if the Nationals aren't hitting home runs, their offense dies:

They are "a free-swinging lineup that is vulnerable to extended slumps because they don't find enough ways to score when they aren't slugging," said one National League scout, who spoke on the condition of anonymity so he could talk more freely about an opposing ballclub.

As Wagner notes, the Nationals have been hit pretty hard with injuries, which has affected their consistency. While some of those returning bats have faired well at hitting home runs, they're not getting regular hits. Ian Desmond has 15 home runs on the year, but is hitting just .225; Ryan Zimmerman has nine homers on the year, four since the All-Star break, but is hitting just .219.

The proof of the Nationals' struggles can be found in the stats. Since the All-Star break, the Nationals are 11-20 and hitting an MLB-worst .223. For the year, the Nationals are 24th in MLB in batting average at .247, but are slightly better in slugging percentage at .391, 19th in MLB. They also are 11th in home runs with 117, but just 27th in hits with 967.

More advanced numbers also show the Nationals struggle to score when they're not slugging. They're just 19th in weighted on-base average, which takes into account the value of different hits, according to Fangraphs. Where their power is evident is their ranking in home run-fly-ball ratio, where they rank 8th in MLB. The Nationals' offense does well when they can actually get under a ball and hit it into the air.

All of this puts a ton of pressure on Bryce Harper, who could be an MVP candidate if the Nationals were better. He's only one of two players on the team hitting over .300 with over 300 at-bats. Take a look at the team's offensive leader board (via ESPN):

The Nationals are 18-8 when Harper hits a home run, creating a small snapshot of how important homers are to the team.

This, of course, isn't their only problem. Wagner also mentions that the team built a roster around injury-prone players. They counted on them either being healthy, or returning to full power when they were healthy. Instead, that hasn't been the case.

While their pitching is an issue, teams like the Blue Jays - MLB's best offense through the trade deadline - proved that teams can scrape by with elite hitting and subpar pitching and defense, at least for portions of the season. This may not result in a trip to the World Series, but it can put a team in playoff contention.

Instead, the Nationals and their $165 million payroll of should-be stars have are in real danger of missing the playoffs entirely.