After Cincinnati forced him to throw 22 pitches in the inning, Alcantara needed 83 the remainder of his outing.
Aguilar put Miami ahead 1-0 with his solo shot in the fourth. He drove a slider from Reds starter Mike Minor into the seats in left for his 13th homer and the Marlins’ first lead in the series.
Garrett Cooper’s two-run double in the fifth made it 3-0. Williams hit a one-out single, stole second and was in the front end of a double steal after Billy Hamilton walked.
Minor (1-8) was lifted after 5 1/3 innings. The left-hander allowed three runs, five hits, walked three and struck out six.
The Marlins activated Cooper from the injured list while the Reds recalled SS José Barrero from Triple-A Louisville.
Reds: The return of C Aramis García will be delayed after an MRI revealed a fracture of his bruised left middle finger.
Marlins: OF Avisaíl García (left hamstring strain) was placed on the 10-day injured list. García exited in the third inning Tuesday.
Neither club has announced the starter for the opener of its next series. The Reds will continue their 10-game road trip Friday at Milwaukee, while the Marlins begin a three-game set Friday at the Chicago Cubs.