The Cubs placed Boxberger on the 15-day injured list Saturday with a right forearm strain, Meghan Montemurro of the Chicago Tribune reports.
Boxberger already missed nearly four months earlier this year due to a forearm injury, and his latest trip to the injured list will keep him out for the rest of the regular season and the first part of a potential Cubs playoff run. Keegan Thompson was recalled from Triple-A Iowa to fill Boxberger's spot in the bullpen.