Marlins ace Jose Fernandez gave up one run in 4 1/3 innings while stretching his pitch count to 73.
Miami has already named Fernandez as its Opening Day starter. The right-hander was throwing hard, at 93-97 mph, but early on he was struggling with command, as he walked four to go along with his four strikeouts.
Nationals manager Matt Williams has not officially announced Strasburg as the Opening Day starter, but the hard-throwing right-hander is believed to be the choice.
Strasburg gave up two singles, including one to Rafael Furcal to lead off the first inning. But the ace was never really in trouble, and his afternoon was finished after 61 pitches. Strasburg's fastball was between 93-96 mph.
The Nationals got to Fernandez for a run in the third inning on Zimmerman's sacrifice fly to left. Will Rhymes walked to open the inning, and he moved to third on Danny Espinosa's double.
"It was not my best," Fernandez said. "I was battling a little bit through it. I gave up only one run and kept the damage small. Obviously, not my best day, but I'm not worried about it or anything."
Fernandez was at 67 pitches through four innings, and he came out for the fifth to face one batter. He struck out Anthony Rendon.
Reliever Dan Jennings was hurt by an error that allowed Espinosa to reach, and the second baseman scored on Wilson Ramos' two-out single.
Up next: The Marlins have another split-squad day Sunday, but neither game will be at Roger Dean Stadium in Jupiter. Kevin Slowey will start at Fort Myers, Fla., against the Twins, who are going with Ricky Nolasco, the Marlins' all-time wins leader. Slowey is a former Twin. The game will be on MLB.TV, and it will be the Marlins' second game where instant replay challenges are available. Also on Sunday, the Marlins wrap up their two-game exhibition against the Yankees in Panama. Nathan Eovaldi will start against CC Sabathia.