Brennan will give up his spot on the 40-man roster to left-hander Reiver Sanmartin (hip), who was reinstated from the 60-day injured list. The 28-year-old Brennan had produced a healthy .869 OPS over 117 plate appearances at Triple-A Sacramento in 2026, but he's had far less success over parts of five major-league seasons between stops with the Guardians and Giants, slashing just .263/.301/.365 (86 wRC+).

Just one day after being called up to the big club, Brennan will wind up heading back to Sacramento. The Giants weren't eager to give him a regular run of at-bats in the outfield, and the left-handed-hitting Brennan wouldn't have offered much value in a bench role since he couldn't be platooned with either Drew Gilbert or Jung Hoo Lee. Brennan was swapped off the 26-man active roster in favor of Jonah Cox, who was called up from Double-A Richmond and should be a more useful bench piece due to his right-handedness and ability to play all three outfield spots.