08:03 AM ET 07.01 | San Francisco can bid good riddance to the nutcracker. [Eric Heitmann's] injury is another lasting legacy from Mike Singletary's infamous nutcracker drill. The exercise in which two players clashed into each other and tried to push the other one back, like a pair of mountain rams, resulted in a series of injuries. None more serious than Heitmann's; he felt a tweak in his neck after a nutcracker encounter in last summer's training camp. According to tackle Joe Staley, Heitmann ignored the injury but was slowed by it. The next day in a team drill, Heitmann broke his leg when he wasn't quick enough to escape a falling teammate. The shattered fibula might have prevented possible paralysis with his vulnerable neck. While recovering from the leg injury, numbness and shooting pain persisted from his neck.