One year to the day after Giants third baseman Pablo Sandoval underwent surgery to remove a fractured hamate bone from his right hand, the team announced that Sandoval fractured the same bone in his left hand and will be lost four to six weeks, a ferocious blow to a team already gasping for offense.

Sandoval will undergo surgery in Palo Alto on Friday. Last year he missed 41 games over nearly seven weeks after surgery, but head athletic trainer Dave Groeschner said there is "hope for some optimism" that he can return sooner this time because the fracture occurred in his non-throwing hand.

For the second consecutive season, the Giants are bedeviled with significant injuries to some of their most important players.

Closer Brian Wilson is lost for the year after undergoing Tommy John surgery on his pitching elbow. Second baseman Freddy Sanchez's return from an August shoulder operation has been derailed repeatedly. First baseman Aubrey Huff is on the disabled list with an anxiety disorder, and reliever Jeremy Affeldt sprained a knee when his son leaped into his arms.

Sandoval's injury might be the toughest for the Giants to overcome. He is their best offensive player who had a 20-game hit streak this season. He has five of the Giants' 21 home runs and accounted for 15 of their 90 RBIs. No other Giant has as many as 10 RBIs.

"The best way to describe it is, it's a bummer," first baseman Brandon Belt said. "He's one of the best hitters on the team and a leader on the team. He helps us win a lot of ballgames. We're going to miss him a lot for the time he's lost."