What position did Jack Lambert primarily play?

What position did Mike Singletary primarily play? Mike Singletary is best known for playing with which NFL team? Which college was Mike Singletary playing for when he entered the NFL? What jersey number did Mike Singletary wear with the Bears? Jack Lambert is best known for playing with which NFL team? Which college was Jack Lambert playing for when he entered the NFL? What jersey number did Jack Lambert wear with the Steelers? What position did Joe Greene primarily play?