The Marlins, who are in last place in the National League East, will start left-hander Wei-Yin Chen (4-10, 5.32 ERA).
Washington, which is third in the same division, will start left-hander Tommy Milone (1-1, 5.24 ERA).
Chen has been strong at home but is 1-6 with a 10.27 ERA on the road.
Milone has a 5.54 home ERA and a 7.04 ERA at night, both ominous signs regarding Saturday's start.
Chen will face a dangerous Nationals lineup that features six-time All-Star and 2015 NL MVP Bryce Harper, who is in his prime at age 25.
The Marlins also have to be wary of teen-aged sensation Juan Soto, 19, a prime candidate for Rookie of the Year.
If that's not enough offense, the Nationals also boast shortstop Trea Turner, who leads the majors with 32 steals; third baseman Anthony Rendon, who won a Silver Slugger award in 2014; second baseman Daniel Murphy, who is a three-time All-Star and the MVP of the 2015 NLCS; catcher Matt Wieters, who is a four-time All-Star; right fielder Adam Eaton, who twice led the American League in triples; and first baseman Ryan Zimmerman, a two-time All-Star.
But even with all that firepower, Murphy seems to be most impressed with Soto.
"He's special," Murphy told mlb.com. "His swing is so fundamentally sound that he can do damage from foul pole to foul pole. That is unique for anyone, much less a 19-year-old.
"It seems like he rarely goes out of the zone. He takes his walks and doesn't strike out a lot. It's really special to watch."
The Nationals (62-61) are looking to recover from a poor 2-5 road trip.
Washington's bullpen isn't in great shape as six of its relievers are on the disabled list, including All-Star Sean Doolittle and set-up man Kelvin Herrera.
The Nationals are facing a slumping Marlins team. Miami (48-76) has lost 15 of its past 17 games, including a season-high-tying six straight. The Marlins have also lost 12 straight road games.
Washington's Max Scherzer, who leads the majors with 16 wins and also tops the strikeout charts, beat the Marlins 8-2 on Friday night.
Marlins manager Don Mattingly was ejected in the fourth inning of Friday's game after he argued a called third strike on Miami hitter Derek Dietrich. Mattingly was upset about a pair of outside pitches given to Scherzer, who clearly needs no assistance to be dominant.
"I was frustrated," Mattingly said. "That wasn't the whole game. ... But you get tired of seeing it, and (Scherzer) doesn't need any help, especially on two 3-2 (counts). It wasn't fun to watch."
The Nationals slugged two homers on Friday -- solo shots by Zimmerman and Wieters -- and took advantage of a pair of Marlins errors.
Rookie left fielder Austin Deal was a bright spot for Miami, making his first major league a solo home run.
"It was good to see him get his first hit," Mattingly said of Dean. "He's had a good season (in the minors). The ball jumps off his bat. He is short to the ball. He has a chance to have success here."