It’s the most pervasive question in Washington this summer, at least in the realm of sports: What happened to the Nationals?

The answer isn’t nearly as simple as many would like.

If only there was one concrete reason for the Nationals’ slow descent from division favorites to a sub-.500 club trying to hang on for dear life. But the truth is, a combination of things had to come together this season to create this mess. Alter any one of them, and the story of the 2018 Nats might be totally different.

On this off-day, with a last-ditch series against the Phillies set to begin Tuesday, let’s run through all the reasons and try to make sense of a season that hasn’t made much sense at all. These are not presented in order of significance.

INJURIES

Yes, every team deals with injuries, but the Nationals legitimately have dealt with more than most. According to rosterresource.com, the Nats have had 25 separate disabled list stints this season, and their 10.10 “roster effect rating” ranks third in the majors, behind only the Angels and Mets.

Here’s the key: The injuries have consumed certain parts of the roster at the same time, severely depleting those units. The lineup was decimated early on without Daniel Murphy, Adam Eaton, Ryan Zimmerman, Howie Kendrick and Matt Wieters. The rotation became a shell of itself when both Stephen Strasburg and Jeremy Hellickson went on the DL in early June. And now the bullpen is a mess with Sean Doolittle, Kelvin Herrera and Ryan Madson all out at the same time.

Yes, the 2017 Nationals dealt with a lot of injuries as well (they rated fifth in the majors in roster effect rating). But those injuries were more spread out among positions and didn’t quite test the club’s depth to the same dramatic extent.

LACK OF ROTATION DEPTH

This felt like a problem area going all the way back to spring training. And sure enough, it has proven to be a significant problem. The Nationals opened the season with A.J. Cole as their fifth starter, then designated him for assignment after Hellickson joined the rotation in mid-April. Erick Fedde was going to be the sixth man waiting at Triple-A if needed, but he has made only six starts and has spent the last seven weeks on the DL with a shoulder injury.

So the Nats have been left to give 10 starts to Jefry Rodriguez, Tommy Milone and Austin Voth, who collectively have a 6.07 ERA. The issue has become only more significant, as Strasburg has missed the better part of 2 1/2 months with shoulder and neck injuries and Gio Gonzalez has gone 1-8 with a 7.07 ERA over his last 13 starts.

The biggest shame of all? Edwin Jackson, who opened the season in Syracuse but opted out of his contract on June 1 (days before Strasburg and Hellickson got hurt), now has a 2.58 ERA in 10 starts for the blazing-hot Athletics.

THE CATCHING PROBLEM

Yes, here’s another area that everyone knew was a problem last winter but wasn’t adequately addressed before opening day. The Nationals had the majors’ least-productive catchers in 2017. Wieters, who was under contract for $10.5 million, wasn’t going to be dropped. But the hope was that he would have a solid No. 2 to help out and potentially take over as the No. 1, if merited.

The problem: Miguel Montero was signed shortly before spring training, then was dumped only a week in after going 0-for-11 at the plate. Pedro Severino, the organization’s longstanding hope for catcher of the future, was abysmal, hitting .171 with a .510 OPS over 203 plate appearances, and was sent back to Syracuse. Spencer Kieboom, the 27-year-old rookie, has done his best to help out Wieters, but while he has done a nice job behind the plate, he’s severely lacking at the plate.

Wieters, to be fair, has turned it around of late and is batting .375 over his last 11 games. But over the big picture, the Nationals still have the least productive catchers in baseball for the second straight season.

LACK OF EXPERIENCED LEFTIES

The Nationals opened the season with four left-handers in their bullpen. That should be a sign of strength, but it wasn’t. Doolittle wasn’t a problem; he was one of the best closers in the majors before injuring his foot in July. But the club’s three other southpaws (Sammy Solís, Matt Grace, Enny Romero) didn’t have much track record and didn’t perform well when called upon to get big outs late.

Grace has shown himself to be the most effective of the group, though more as a full-inning or even long reliever than as a matchup lefty. Solís continues to aggravate with his struggles in big spots and just earned his second demotion of the summer. Romero had a great arm, but was dumped after only two appearances and has now pitched for the Pirates and Royals this season, as well.

Tim Collins has done better when given a chance, but the Nationals’ lack of a lockdown lefty (a position that doesn’t usually cost much) has proven to be a major problem all season.

A ROOKIE MANAGER AND NEW COACHING STAFF

Yes, Davey Martinez has to be included in any discussion of what has gone wrong this season. Some will argue he’s the No. 1 reason for the Nats’ struggles. The take here is that’s not a fair assessment. No manager (even Dusty Baker) could overcome all the aforementioned issues and run away with the division this year. Also, Martinez genuinely seems to be liked and respected by the vast majority of the clubhouse.

That said, has the rookie skipper made some rookie mistakes? Yes. His bullpen management has left something to be desired. (Though, to be fair, there are very few managers truly effective in this department.) His ever-changing lineup combos haven’t helped that group find some needed stability.

Any discussion of the manager, though, also has to include his coaching staff. Remember, the Nationals didn’t just fire Baker, they fired the entire staff except for third base coach Bob Henley. The Mike Maddux-Derek Lilliquist swap seems to have had a negative effect, with few pitchers ever even mentioning their position coach when discussing matters positive or negative. (Maddux’s name used to come up all the time.) Hitting coach Kevin Long gets more positive reviews from his players, and the resurgence of the lineup now that that group is healthy has taken some heat off Long. But defense and baserunning remain problem areas for this team, and the coaching staff almost always deserves some of the blame when that happens.

THE MUCH-IMPROVED BRAVES AND PHILLIES

One reason the 2017 Nationals were able to run away with the National League East despite injuries to their lineup and ineffectiveness of their bullpen in the first half was the simple fact no one else in the division was ready to challenge them. The Mets once again were hoping for the impossible: a healthy rotation and lineup despite all kinds of injury histories. The Braves and Phillies weren’t ready to contend yet. The Marlins were ... well, the Marlins.

That’s not the case this season. Atlanta and Philadelphia each entered the season with reason to believe improvement was coming. Consensus opinion was that both teams were probably another year away (moreso in the Braves’ case) but it turns out both teams were ready to win now.

And so here we are on Aug. 20, and it’s the Braves and Phillies sitting atop the division, preparing to engage in a compelling pennant race with each other, while the Nationals are stuck seven games back, hoping they haven’t run out of time to thrust themselves back into the mix.