Pittsburgh second basemen Freddy Sanchez's sore shoulder could keep him out on Opening Day, so the Pirates signed infielder Luis Rivas for insurance, according to the Associated Press. "When I hit, it's fine. When I run, it's fine. Even when I throw lightly, it's fine. It's not until I throw hard, I try to let it go, that it doesn't cooperate," Sanchez said. "That's why I'd rather take more time off now, than go through the whole season like this because this is not fun." Sanchez is not expected to play in the field for the next few days, but he will taking batting practice. The Pirates will open the 2008 season on Monday March 31 in Atlanta.