Horwitz is out of the lineup for Wednesday's game against the Rockies.
As is usually the case, the left-handed-hitting Horwitz will be left out of the starting nine while the Pirates face a lefty starter (Jose Quintana). Jared Triolo will step in at first base in place of Horwitz, who has gone 3-for-13 (.231 average) with four walks against lefties this season.