First baseman Nathaniel Lowe on Monday formally signed with the Boston Red Sox, the club announced.

The deal, which is for a prorated portion of the major league minimum after Lowe was designated for assignment by Washington earlier this month and went unclaimed on waivers, adds a veteran bat to a first-base mix that has been uncertain since Triston Casas' season-ending knee injury in May. In announcing a series of moves, the club said Lowe will wear No. 37.