Miguel Rojas capped a three-run rally in the ninth inning Monday, allowing the Marlins to overcome a 4-2 deficit and beat the Giants for the fourth time in five games over the past eight days.
All four wins have come in come-from-behind fashion.
Monday's thriller could have a carryover effect on the rest of the series as Giants closer Hunter Strickland and Marlins outfielder Lewis Brinson, one of the heroes of the ninth-inning rally, exchanged words after the Marlins had taken the lead.
Brinson also had a hand in one of Miami's rallies last week, smacking a game-tying hit off Madison Bumgarner in last Monday's 7-5 win.
The Giants did not appreciate the way Brinson celebrated the hit, and it was no surprise when Strickland's first pitch to him in the ninth this time around was under his chin.
But Brinson earned the right to celebrate again, lining a game-tying single to right field off Strickland, then yelling at the Giants? enforcer on his way to first base.
Brinson reached third on Rojas' tie-breaking hit, after which Strickland was removed from the game, exiting the field toward the third base dugout and within 15 feet of Brinson.
The two then exchanged words again, setting the stage another possible encounter before the end of the series.
It was Strickland's fourth blown save of the season, but just the Giants first loss this season in a game in which it led going into the ninth inning. They'd been 31-0.
Afterward, Giants manager Bruce Bochy credited for Marlins for once again not going down without a fight.
"We've had the lead; we've got to finish it," he said. "They keep themselves in the ballgame. Keep it close and anything can happen."
Monday's 5-4 outcome was identical to last week's 5-4 Marlins win on Wednesday, a game also started by left-handers Caleb Smith of the Marlins and Andrew Suarez of the Giants.
Tuesday's second game of the series also will feature a pitching rematch, with right-handers Dan Straily (2-2, 4.23) of the Marlins and Dereck Rodriguez (1-1, 4.34) of the Giants going head-to-head for the second time in six days.
The Giants prevailed the first time around last Thursday despite blowing an early 3-0 lead. They needed 16 innings to win 6-3.
Rodriguez worked 6 2/3 innings in the win, allowing two runs and seven hits. It was just the third start and fourth big-league appearance of his career.
He'll take an 0-0 and 2.70 ERA against the Marlins into the game.
Straily, meanwhile, worked five innings in the first meeting, allowing three runs and three hits. Andrew McCutchen and Mac Williamson accounted for the three runs with home runs.
The 29-year-old has never lost to the Giants, going 4-0 with a 2.82 ERA in six career starts. He's 2-0 with a 1.13 ERA in two starts in San Francisco.