Johnston is absent from the lineup for Wednesday's game in San Diego.
The Padres are going with a lefty opener (Kyle Hart) before turning to a right-handed bulk reliever (Griffin Canning). While the left-handed-hitting Johnston will begin the contest on the bench, he's a candidate to enter mid-game when Canning or another righty takes over. Colorado has Jake McCarthy in right field and Hunter Goodman at designated hitter.