In 14 innings of a doubleheader Friday, in a season that has become a glance at the future, the Washington Nationals could appreciate a few finer details of the opener at Marlins Park. They couldn’t say the same of the nightcap.

In the first game, the Miami Marlins first sent out Sixto Sánchez, a rookie who, since debuting against the Nationals in August, has treated the majors like a personal playground. But some of Washington’s youngest players, the ones who could face Sánchez for years to come, laid the groundwork for a win. Luis García, Carter Kieboom and Victor Robles combined for four hits, a walk, three runs and three RBI off Sánchez, who was outlasted — and entirely outdone — by Erick Fedde in a 5-0 win.

Then Washington dropped the second leg, 14-3, after rookie right-hander Wil Crowe hit a wall and the bullpen lapsed.

Fedde, 27, turned in his best start of the season, yielding just one hit in six scoreless innings. He struck out six and submitted an early audition for the 2021 rotation. The 26-year-old Crowe, on the other hand, was pulled after 2⅓ innings, threw more balls than strikes and inspired little confidence while allowing six runs and walking two.

“The second game wasn’t as clean,” Manager Dave Martinez said. “But the first game went really well. Fedde threw the ball really well.”

The Nationals (19-30) remain in last place but arrived in Miami with a chance to play spoiler. That’s not the role they wanted this September, especially coming off their first World Series title. But at the end of a down summer, with a growing number of key players on the injured list, that’s what Washington had to settle for with 10 days left in the season.

The Nationals are set to play 13 games in that stretch, with five against the Marlins this weekend, then four vs. the Philadelphia Phillies, then four vs. the New York Mets. Each of those clubs is vying for a playoff spot. The Marlins entered this series in second place in the National League East, good for automatic entry. Either the Phillies or the Mets could catch them or take one of two wild-card spots. And the Nationals could make it difficult for all of them.

On Thursday, as it rested between trips to Tampa and Miami, Washington placed Adam Eaton on the 10-day IL with a fractured left index finger. That will end his season with a quiet thud, and the 31-year-old could be finished with the Nationals. They hold a $10.5 million club option for next season and could decline.

“It’s fitting, for how my year has went, to end on that note,” Eaton said a few hours before first pitch. “On a personal level, with the contract next year, to do what I did this year and to end up on IL at the end of the year is just as fitting as could be.”

But the doubleheader disrupted that narrative for the Nationals. Sánchez entered with a 1.69 ERA in 32 innings, and he continued that success by holding Trea Turner, Juan Soto and Asdrúbal Cabrera to no hits and an intentional walk in six plate appearances. He just couldn’t handle the rest of the lineup.

In the fourth, Washington scored three runs in the span of five batters. It began with Yan Gomes’s second hit of the evening, a bouncer against the shift. After that, García collected his second single, Kieboom walked, Andrew Stevenson plated two runs with a single and Victor Robles brought in another with a blooper to left. Fedde took it from there.

He didn’t allow a hit until the fourth. He stranded a runner in each of his last three innings. In all, Fedde got 11 called strikes on 47 sinkers. That pitch maxed out at 96 mph, a high velocity for him, and he mixed it with a balanced diet of curveballs, cutters and change-ups. He threw 91 total pitches and completed six innings for the second time this year.

“It’s just one of those days where you have four pitches,” Fedde said. “You know, you love those days.”

“It’s just a matter of him knowing that the two-seamer he’s throwing is very effective,” added Gomes, who caught Fedde’s gem. “The only talks we had about it today were: Let’s just get early outs.”

Crowe could not replicate Fedde’s success. The Nationals grabbed a 2-0 first-inning lead that quickly disappeared. Corey Dickerson tagged Crowe with a leadoff homer to right in the bottom half. Brian Anderson started the second with a solo shot to left. And in the third, his final inning, Crowe lost control.

The Marlins scored four runs against a mix of Crowe and Kyle McGowin, but all of them were charged to the starter. With one out, he gave up back-to-back singles before issuing back-to-back walks. That’s when McGowin relieved him, nearly left the bases loaded, then had the inning extended when catcher Kurt Suzuki dropped a flip at home plate.

“I fell into a habit of getting too quick, I feel like, and then I do it in the windup and in the stretch,” Crowe said of why he is lacking command. “I’ve been working on it for the last two weeks.”

Washington never recovered despite Soto scoring Robles in the fifth with his second of three hits on the day. The progress was unwound when Anderson rocked a three-run homer off rookie James Bourque in the bottom half. The deficit ballooned in the sixth when Brock Holt, an infielder, relieved Aaron Barrett and Anderson crushed his third blast of the game. The Marlins tallied four runs before Holt walked off the mound.

Crowe has struggled to throw strikes through three major league appearances. He managed just 29 in 62 pitches Friday. On the season, he has thrown 106 in 194 total pitches. That, among other factors, was why he couldn’t join Fedde, García, Kieboom and Robles as reasons for the Nationals to look ahead.

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