(San Francisco, CA) -- The San Francisco Giants are losing their first baseman right before they head into the postseason. The Athletic reports Brandon Belt suffered a fractured left thumb after he was hit by a pitch in Sunday's game. An X-Ray revealed the fracture and it's expected he will miss the remainder of the regular season. The 33-year-old will meet with team doctors this week to determine a timetable for his return. Belt leads the Giants with 29 home runs this season, while batting .274 with 59 RBI.