Sewald was optioned to Triple-A Las Vegas on Thursday, Anthony DiComo of MLB.com reports.
Sewald allowed a run on a walk and a single in Thursday's loss to the Rockies, raising his season ERA to 4.85 and prompting the Mets to send him to the minors to work through some of his struggles. Given the injuries and ineffectiveness hampering the team's bullpen, Sewald figures to rejoin the big-league team once he's able to figure some things out. A corresponding roster move will be announced prior to Friday's series opener against the Dodgers.