Sandoval (biceps) allowed one hit and one walk while striking out seven over five scoreless innings for Double-A Portland on Saturday.
Sandoval got up to 68 pitches (43 strikes) and, per MLB.com, the Red Sox anticipate him joining the rotation for their final series before the All-Star break. The left-hander is expected to fill in for injured starter Connelly Early (elbow) for at least one start.