Giants manager Bruce Bochy challenged the call but the play was confirmed after one minute and 18 seconds. The Giants eventually lost the game, 3-2.
"I didn't see the replay but I had nothing to lose at that point," Bochy said. "Buster thought he might have got there, so it was a no-brainer. At that point, I hadn't used a challenge and [was] hoping we could get good news."
The Giants were down by one run when the play occurred. Posey had gotten on base in all three of his previous plate appearances and had driven in both of the Giants' runs with a double in the third inning.
Had the call been overturned, Marlins pitcher Bryan Morris would have had to face Pablo Sandoval, who entered the game 8-for-24 with two RBIs with a runner on first and two outs.
Maria Torres is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.