Nationals catcher Wilson Ramos hauls in a pop-up hit by the Marlins’ Adeiny Hechavarria in the third inning. (Alex Brandon/Associated Press)

Blame for the Washington Nationals’ mediocrity has most often been placed on poor health, but their injuries were irrelevant at the most pivotal moment Wednesday night. They loaded the bases with no outs in the eighth, they needed one run to snap a tie and no replacements or fill-ins loomed. Due up were Anthony Rendon, Jayson Werth and Adam LaRoche.

“Those are the three guys I’d want up there every single time in that situation,” outfielder Nate McLouth said.

The Nationals’ sixth loss in seven games, an 8-5, 10-inning stomach punch against the Miami Marlins at Nationals Park, may have been their most difficult yet to bear. They erased a 4-0 deficit with a spirited comeback against the soft underbelly of Miami’s bullpen, which entered only after starter Henderson Alvarez exited with a stiff elbow. They would lose when Aaron Barrett and Jerry Blevins, both excellent all year, yielded four runs in the 10th.

The root of their loss, though, lay in their squandered chances, none more costly than the face-palm eighth inning. With the bases loaded and no outs, Rendon, Werth and LaRoche made consecutive outs — strikeout, pop-up, groundout — and managed to score zero runs. The Nationals put 19 men on base in the final six innings, and only five scored. No wasted chance hurt worse than the eighth.

“It’s frustrating,” Manager Matt Williams said. “Everybody’s frustrated by it, but there’s nothing we can do about it now except prepare for Friday. Certainly to have a chance like we had with the bases loaded, nobody out, you want to score that run. Didn’t happen tonight. So we’ll keep pushing. Keep playing hard. They battled back, tied it. Just couldn’t get it done.”

Heroic performances and mind-numbing moments stacked up like cordwood. Jordan Zimmermann allowed four runs over five innings, another start below his standard. McLouth, maligned for the first two months of his Washington tenure, went 4 for 4 with a walk and a stolen base. Wilson Ramos smashed a game-tying home run in the seventh, squelched a Marlins rally in the eighth with an inning-ending pickoff and was thrown out trying to stretch a double to lead off the ninth.

In the end, the Nationals could only absorb a brutal loss and, three days past Memorial Day, look to the calendar for solace. But how early is it? To reach 90 wins, a threshold that should secure a playoff spot, the Nationals need to win 65 of their remaining 110 games — a .591 winning percentage, or 96-win pace over the course of a full season.

On the flip side, the standings provide little reason for panic. With four months still remaining, the Nationals remain just three games behind the first-place Atlanta Braves. The Nationals’ best hope derives from the fact that they aren’t alone among contenders in their mediocrity.

“This is just a test for us,” LaRoche said. “To see where we’re at mentally and see how bad we want to grind our way out of it and get back in this division. It could always be worse.”

On Wednesday night, the Nationals gave themselves every chance to creep closer to the Braves, only to fritter them away.

In the eighth, McLouth sparked another rally with a gritty at-bat, earning a walk from left-handed reliever Mike Dunn. Once McLouth stole second base, Dunn had no interest in pitching to Scott Hairston, who walked. Denard Span bunted to push the runners up a base. He placed it so well he earned a single.

The Nationals had the bases loaded and no outs. Surely, they would push across at least one run. They had to. Right?

Rendon had the first chance. He fouled off five consecutive two-strike pitches, including one he scalded off McLouth’s big toe in foul ground. But on the at-bat’s 10th pitch, he swung over Dunn’s slider for strike three.

“That’s what we have BP for, for those situations. That’s what we practice for,” Rendon said. “And not to come through is obviously disappointing. That’s why we lost. We didn’t come through in those situations, and they did.”

Next came Werth, the Nationals’ No. 3 hitter in a healthy lineup or not, the perfect man for the spot. He has crushed lefties this season, and in his career against Dunn he had gone 4 for 5 with a homer, a double and five walks. After Werth took one ball, Dunn fired a 95-mph fastball over the plate. Werth skied it up the middle of the infield.

The bases remained loaded, the park grew anxious and LaRoche came to the plate. He fouled off a pair of two-strike pitches, then slapped a harder grounder right to the first baseman.

The Nationals had loaded the bases with no outs, and they forced Dunn to throw 35 pitches in a single inning, and they still could not push across a solitary run.

Both LaRoche and Williams did not fault their execution. Who would blame Rendon for a 10-pitch at-bat? Werth had found a good pitch to hit and just missed it. LaRoche had barreled a ball after fighting off several pitches.

“Some great at-bats,” LaRoche said. “I feel like we all got pitches to hit, and it didn’t happen. We missed ’em.”

Leaving the bases loaded resonated into the 10th. Blevins loaded the bases, and Williams summoned Barrett and his wicked slider. “I’ve been put in those spots all year,” Barrett said. “That’s my job, to leave those guys there.” On this night, he couldn’t. He left sliders high to Casey McGehee and Reed Johnson, and they both whacked them off of the wall.

“That’s my best pitch,” Barrett said. “I wanted him to beat me with him. My last one was probably elevated too much. I paid for it.”