Sanchez felt dizzy after being hit by a foul ball and was pulled from Thursday's game as a precautionary measure, AJ Cassavell of MLB.com reports.
Sanchez is the Padres' backup catcher, so it's entirely possible that he would be absent from the lineup for the next couple days, even if he hadn't been hit by an arrant foul ball Thursday. However, until the club is certain that he's at full health, consider him day-to-day.