Alcantara extended his scoreless string to 18 innings and has completed at least eight innings in four of his past five starts. The 26-year-old allowed six hits and struck out six while lowering his ERA to 1.61.
''I think it's my positive mentality,'' Alcantara said. ''I just want to go out and compete. Sometimes you have bad days, like me. But you can't worry about it because I know I can do better the next time.''
Aguilar's smash against reliever Tanner Rainey (1-2) deflected off second base and rolled into center field, scoring Willians Astudillo from second. Astudillo's run-scoring single to right scored automatic runner Jazz Chisholm Jr. from second to tie it.
For the Marlins, it was their first series victory since winning two-of-three against the Nationals May 16-18.
''It was a very emotional moment that we were able to win,'' Aguilar said.
Chisholm originally was called out, but the Marlins successfully appealed that he beat right-fielder Juan Soto's throw. But the play was overturned because Nationals catcher Keibert Ruiz blocked Chisholm's path to the plate.
''We catch a break and it seems like we haven't caught a break in these kinds of games all year,'' Miami manager Don Mattingly said. ''The baseball gods were looking out for us tonight.''
Ruiz's RBI single against Tanner Scott (2-1) in the top half put Washington ahead 1-0.
''That was a great game tonight,'' Alcantara said. ''Both teams were fighting.''
Nationals starter Josiah Gray pitched five scoreless innings but was lifted after a season-high 101 pitches. Gray allowed six hits, walked one and struck out six.
Miami left fielder Jorge Soler misplayed Soto's drive to the warning track that fell for a one-out double in the sixth. Soto advanced on Nelson Cruz's groundout to third, but Alcantara retired Josh Bell on a groundout to second to strand him.
The Marlins loaded the bases with one out in the first, but Gray struck out Avisail Garcia and Jon Berti to end the threat.
The 5-foot-9, 225-pound Astudillo set his sights on home as soon as Aguilar's single reached the outfield.
''I had to score as soon as I saw it leave the infield,'' Astudillo said. ''Whichever way possible, I had to score that run.''
ADON SENT DOWN
In the aftermath of Joan Adon's outing of three-plus innings and eight runs allowed Tuesday, the Nationals optioned the 23-year-old right-hander to Triple-A Rochester. Adon made the opening day roster but has struggled to a 1-10 record and 6.95 ERA in 12 starts. LHP Sam Clay was recalled from Triple-A.
''We want him to work on some things,'' manager Dave Martinez said. ''We had a great conversation (Tuesday), all positive. This kid is going to come back here and help us win games. His stuff is electric. He just has to learn how to use it and use it effectively.''
Nationals: RHP Joe Ross is scheduled to have Tommy John surgery for a second time Friday. ... RHP Victor Arano (left knee bone bruise) is progressing with his rehabilitation
Marlins: OF Jesus Sanchez (right upper back tightness) did not play. Sanchez left in the second inning Tuesday.
Nationals: Sidelined since June 1, 2021, RHP Stephen Strasburg makes his season debut Thursday, when he starts the series finale. The 33-year-old Strasburg has been sidelined for most of the past two seasons and underwent surgery for thoracic outlet syndrome last summer.
Marlins: LHP Trevor Rogers (2-5, 5.80) will make his fifth career start against Washington Thursday.
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