Ian Desmond tosses the bat after striking out to end the eighth inning. (John McDonnell/THE WASHINGTON POST)

Another starting pitcher had been shelled, another position player had limped to the dugout with an injury and the Washington Nationals were a husk of themselves. In the fifth inning Sunday afternoon at Nationals Park, fill-ins and replacements swarmed the field. Ryan Zimmerman and Ian Desmond manned third base and shortstop. The other seven players were reserves or minor leaguers on opening day. The one-time World Series favorite had been reduced to a cast of contingencies.

The undermanned Nationals were resilient Sunday, but not even their four-run eighth-inning rally could prevent a 7-6 loss to the Colorado Rockies — or questions about Manager Davey Johnson’s decision not to employ Adam LaRoche as a pinch hitter.

The day after Dan Haren recorded 10 outs, left-hander Ross Detwiler retired 11 and yielded seven earned runs. The Nationals produced a bushel of base runners and reduced a seven-run deficit to one on a clutch hit from little-used catcher Jhonatan Solano, but they waited too long to accept the Rockies’ invitations to creep back into the game.

The Nationals dropped to 37-38. Baseball’s marathon affords the Nationals time to pull out of their tailspin. Once Bryce Harper and Wilson Ramos return, which should come within the next 10 days or so, their offense can only improve. But the season’s halfway mark looms one week away, and the Nationals still appear a good distance from coalescing into a real, live contender.

“Last year was good, but not many teams play 15 over .500 the whole year,” Zimmerman said. “A lot of teams struggle, go up and down. We need to get to that five, six games over the .500 mark and then go from there. So that’s kind of the goal.”

The queasy notion that the Nationals are not what everyone thought they were has hovered for months, but it had perhaps never been more stark than Sunday. After Jayson Werth left the game with a strained left groin in the bottom of the fourth, the Nationals were left with a consonant-heavy, experience-starved outfield of Steve Lombardozzi (who smacked three hits), Jeff Kobernus and Roger Bernadina.

“We’re past the point now where it’s too late to make excuses with injuries,” Zimmerman said. “We all need to step up and start winning games no matter who’s out there.”

Johnson kept LaRoche and Denard Span on the bench against a left-handed starter for the second time in a week. Johnson had reason to try any means to kick-start the Nationals, and LaRoche and Span have hit .212 and .137 against lefties this year, respectively. But the Nationals, winners of 98 games a year ago, were not expected to turn to Chris Marrero and Kobernus when they were in need of a boost.

Their primary woes Sunday occurred on the pitcher’s mound for the second straight day. Detwiler made his third start since he returned from the disabled list with a strained right oblique. Michael Cuddyer and Nolan Arenado crushed home runs to lead off the second and fourth innings. Detwiler’s trouble otherwise came from seven singles, which led to three runs in the third and another three in the fourth.

“He’s still very young, still learning how to use all the weapons in his arsenal,” Johnson said of Detwiler. “Today, he didn’t feel like he had a good sinker or could locate it real good, so he threw more change-ups. But it’s sequence pitching.”

Detwiler disagreed that his pitch sequencing needed improvement. He saw rotten luck on balls in play as the main culprit.

“They didn’t hit the ball that hard today,” Detwiler said. “There was two hard-hit balls, and everything else just fell in. Maybe look at a guy like [Ian] Krol who strikes everybody out. Maybe I should just start doing that.

The Nationals generated ample chances. They scored twice in the fourth on RBI outs from Marrero and Kurt Suzuki but went 1 for 10 with runners in position and left 10 men on base through seven innings. In the end, they turned 13 hits and five walks into six runs.

The most painful — and strategically intriguing — wasted chance came in the seventh inning. Desmond drew a two-out walk off right-handed reliever Rob Scahill to load the bases for Marrero. Johnson could have sent LaRoche to hit, which would have drawn lefty reliever Josh Outman — who is holding lefties to a .185 average this year— from the bullpen.

Rockies Manager Walt Weiss seemed to anticipate it — he climbed up the dugout steps and took a step out, only to turn around as Marrero strolled into the batter’s box. Johnson wanted to imbue confidence in a young hitter.

“It’s a long season, and some of these guys, I’m not going to just completely take the bat [out of their hand] unless it’s the tying run or something,” Johnson said. “They’ve got to contribute and do the things I know they’re capable of doing. I want to show them I have confidence in them in those situations.”

Marrero could not validate Johnson’s belief. He popped up the first pitch he saw to right field. “I don’t like that he gets the first fastball in the middle and goes the other way with it,” Johnson said.

Afterward, LaRoche did not protest being left on the bench. “If you looked at my pinch-hit numbers,” he said, “I’d probably never pinch-hit again.” In his career, he is 14 for 65 with three extra-base hits as a pinch hitter.

The Nationals finally struck in the eighth, loading the bases with one out against setup man Matt Belisle. Anthony Rendon struck out, but Zimmerman hit a chopper up the middle that shortstop Josh Rutledge kicked into shallow right field. Zimmerman was given a single, and an extra run scored as Rutledge chased down his error.

Weiss called for lefty reliever Rex Brothers to face Bernadina, Werth’s replacement. Johnson countered with Solano, whose last hit came June 12.

“I’m ready all the time,” Solano said.

Brothers left a first-pitch slider up and over the plate, and Solano drilled a double to the left-center field gap. Zimmerman sprinted home from first to slice the Nationals’ deficit to one.

There is probably no hitter they would have wanted at the plate representing the go-ahead run more than Desmond, who has delivered clutch hits all month. But he struck out on three pitches, stranding his fifth runner of the day.

The Nationals, at least, had made their presence felt. But they finished another day having yet to sustain any kind of charge, instead wondering how — and when — it might happen.