The nature of Moustakas' illness was not disclosed. The move was made retroactive to Saturday.
Moustakas was initially in the Reds' lineup for Tuesday night's game against the Arizona Diamondbacks before he was placed on the injured list. Kyle Farmer replaced Moustakas in the lineup as he has been doing so since Moustakas was first scratched from the Reds' lineup on Friday against the Cleveland Indians.
Moustakas has two homers and five RBIs in 12 games this season and is slashing .289/.404/.553.
The Reds reinstated infielder Alex Blandino from the injured list in a corresponding move.