The right-hander gave up two hits, both to Marlins leadoff man Jake Marisnick, and hit one batter. Fister struck out four and induced a double-play grounder, showing his trademark sinker.
"It's knocking a little bit of rust off, but everything felt very good," Fister said. "It's relieving to get out there and feel good. All the work we've been putting in, trainers and pitching coaches and everybody, it's paying off and we're on the right track."
Bryce Harper was hitting .167 with one extra-base hit coming into play, but he led off the fourth inning by cranking a double into the right-field corner off Alvarez. Harper moved to third on a wild pitch and scored on Wilson Ramos' sacrifice fly, giving the Nats a 2-0 lead. Harper singled in his next at-bat and finished 2-for-4.
After the Marlins' Marcell Ozuna hit his second spring home run, off Rafael Soriano in the top of the seventh, Adam LaRoche and Espinosa started the bottom of the frame with back-to-back shots against Kevin Slowey. LaRoche lifted his into the wind and out to left field, while Espinosa -- battling for a job -- ripped his first of the spring out to right-center while batting left-handed.
Alvarez struck out three of the first four batters he faced before running into some trouble. He got out of a two-on, two-out jam in the second before the Nats got on the board in the third. With one out, Denard Span and Ian Desmond hit consecutive singles and moved up on a passed ball. Right fielder Reed Johnson then dropped Jayson Werth's short fly ball for a run-scoring error, although Werth was credited with an RBI.
Alvarez got through four innings, giving up two runs (one earned) on five hits, with one walk and four strikeouts.
The Marlins tied the game in the eighth against Ross Detwiler, who was making his second appearance since learning he was being sent to the bullpen. The left-hander walked two and gave up two hits, with Donovan Solano hitting an RBI double and Ozuna contributing a sac fly.
Up next: Jacob Turner, lined up as Miami's No. 4 starter, will face the Tigers in Lakeland, Fla., at 1:05 p.m. ET. The 22-year-old right-hander is out of options, and there has been some trade speculation involving him. Turner's start will be closely watched, although he is expected to remain with the Marlins. Ed Lucas (left hamstring) is making his return to the lineup, and he will play first base. Lucas is competing for a bench job. Drew Smyly will start for the Tigers.