Casas will not start Monday in Baltimore, Jen McCaffrey of The Athletic reports.
The top four in Boston's order hit a combined .138 (9-for-65) during a season-opening series that saw the Red Sox lose three of four games in Texas. Casas, who was 1-for-16 with seven strikeouts, will get the day off against Baltimore lefty Cade Povich, the first southpaw starter the team will face this season.