The Athletics-Marlins game was halted for 10 minutes Sunday while medical personnel treated two fans hit in the face by the same foul ball.
A line drive off the bat of Oakland's Nick Punto struck a young woman sitting in the first row along the right-field line, and then hit a man nearby.
The woman was conscious when she was placed in a wheelchair on the field and taken along the warning track to an exit in the right-field corner. She was taken to a hospital for evaluation, the Marlins said.
The man received treatment at the ballpark and was released.
"Marlins Park was a dangerous place today," Miami manager Mike Redmond said. "I saw the girl get hit square on. She had no idea it was coming. I think she just turned at the last second."
Punto said his foul skipped off the railing along the front of the stands before hitting the woman.
"It's very unfortunate," he said. "I hope she's doing OK. I'll be reaching out."