WASHINGTON — A Phillies season that started with such promise became just another season that fell short of October, as the Phillies were eliminated from playoff contention Tuesday afternoon with a 4-1 loss to the Nationals.

The Phillies, by losing the first game of a day-night doubleheader, will miss reaching the postseason for the eighth straight season. They have lost 12 of their last 19 games and will need to win three of their final six just to secure their first winning season since 2011.

“It’s disappointing,” Rhys Hoskins said. “You set out at the beginning of the year, the beginning of the offseason, spring training, whatever it may be with the goal in mind, right? Obviously, we’ve come up short this year.”

They added five All-Stars this offseason, invested nearly a half-billion dollars in their roster, introduced Bryce Harper on top of the dugout in Clearwater, Fla., and started the season with a sweep of the Braves. It was a perfect beginning, but now the Phillies will spend the final week battling for .500.

The Phillies used seven pitchers in the loss. They started reliever Blake Parker, who gave the Phillies two scoreless innings in a bullpen game. They scored in the first inning, but had just one runner in the final eight innings reach scoring position and their last 18 batters went down in order.

Gabe Kapler has talked a lot this month about seeing fight in his team, but has he seen enough fight?

“Oh, yeah,” Kapler said. “And sometimes it’s a little bit too much fight. Sometimes it’s a little bit too much … there’s a lot of pressure. Our guys want to perform so badly. And I appreciate and respect that about them. And sometimes they put a little additional pressure on themselves. I think that’s what we’re seeing right now.”

Cleanup hitter Brad Miller was ejected in the sixth inning after being called out on strikes, Edgar Garcia walked the first three batters he faced in the eighth before allowing a run, and it was a listless end to the team’s playoff dreams.

“We’re going to have plenty of time to reflect on the fact that we didn’t get to the postseason, which was the goal and the only thing that we thought about all season long. And we will get to that moment of reflection,” Kapler said. “It’s felt some sting already. I think we’ll continue to feel some sting. We have a game to get ready for right now and that’s important, but certainly there will be time to reflect.”

Aaron Nola will start the nightcap against Max Scherzer, who can pitch his team to the postseason if the Nationals win and Cubs lose.

The Phillies bullpen was ravaged by injuries, but it was the bolstered lineup’s failure to hit for power and the front office’s decision to bet on the starting rotation that sank the season. The Phillies entered Tuesday with the 19th-best slugging percentage and eighth-fewest home runs in MLB. Their starting rotation had the 17th-best ERA and accumulated the eighth-lowest WAR.

“I think it’s a lot of things, honestly,” Hoskins said. “We haven’t been as consistent as a team as you would have hoped throughout the year. We pitched well throughout the year and we hit throughout the year but it never seemed to sync up for a long period of time. Yeah. I guess that’s what I would pin it on.”

The Phillies thought they had built a playoff team. They believed in their young rotation. But even if they stumbled, they were confident that their lineup would outslug opponents. Instead, the rotation crumbled and the lineup showed little muscle.

They led the division by three games on June 1. They have played .465 baseball in 99 games since and trail the division-champion Braves by 16½ games.

The morning after Harper signed, Rhys Hoskins looked to a picture of the 2008 World Series celebration and said he did not want to hear about that moment anymore.

“I want to feel it,” Hoskins said in March. “I think we’re on our way.”

The Phillies had a historic offseason. Harper would be introduced a few days later on top of the team’s dugout in Clearwater. The Phillies were buzzing.

Six months later, their playoff hopes ended with another lackluster loss. The buzz felt during spring training had been gone for weeks.

The Phillies did not build a playoff team this season, and they’ll find out this week if they even have a winning one.