Dee Gordon had an RBI triple and scored on a wild pitch off Nick Masset in the sixth inning for Miami.
Chen breezed through the first two innings, retiring six straight with a strikeout on 17 pitches with 14 strikes. But with one out in the third inning, the Nationals strung together five straight hits. The big blast was Taylor's three-run, opposite-field home run.
Ben Revere added an RBI single, and Bryce Harper had a single to left in the inning.
Chen, Miami's expected No. 2 starter, worked four innings, allowing four runs on seven hits with a strikeout.
"At first, I was just trying to get ahead in the count, and they were swinging early, so I got the first couple of outs quickly," Chen said through his interpreter. "After a couple of innings, I started to work on my changeups. So I started to throw in either strike one or strike two in the counts. Maybe I didn't have such good control on my changeup yet."
Blake Treinen made the start for Washington in place of Bronson Arroyo, who was scratched due to a sore right shoulder. A source tells MLB.com's Bill Ladson that Arroyo has a tear in his labrum, which the club has not confirmed.
Treinen, who was pitching for the first time in a week after battling an issue with his right middle finger, threw two scoreless innings in his spot start. The right-hander ran his fastball in the 94-96 mph range, striking out four while allowing one hit and a walk.
"That's the kind of outing that I definitely can build off of," he said. "Everything felt really good, it was a promising outing for me."
Harper went 1-for-4 and Danny Espinosa was 2-for-3, breaking an 0-for-17 stretch to start the Grapefruit League season, for Washington.
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Marlins right-hander Jarred Cosart, in the mix for a rotation spot, entered in the top of the fifth and threw three shutout innings, allowing two hits with a walk and a strikeout.
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Up next for the Nationals: Stephen Strasburg will make his third Grapefruit League start of the year when the Nationals host the Braves at Space Coast Stadium on Thursday at 1:05 p.m. ET. In his first two starts, Strasburg has allowed three runs in five innings and struck out six. He is scheduled to throw four innings Thursday.
Up next for Marlins: A couple of All-Stars will be on the mound Thursday for the St. Patrick's Day matinee at Roger Dean Stadium. Miami is sending ace Jose Fernandez, its expected Opening Day starter, to the hill for the 1:05 p.m. ET contest to air on an exclusive free audio webcast. Jacob deGrom will go for the Mets. Scheduled to play for Miami are Ichiro Suzuki, Marcell Ozuna, Christian Yelich and Giancarlo Stanton. Jeff Mathis is lined up to catch.