He suffered a partial dislocation and a trainer appeared to have popped it back in. McCarthy recorded the out, which was the last of the bottom of the fifth inning.
The Braves said McCarthy is day-to-day.
Left-hander Sam Freeman replaced McCarthy on the mound to start the bottom of the sixth.
Last season with the Los Angeles Dodgers, McCarthy dislocated his left shoulder during a kettlebell exercise and landed on the disabled list.