The short mud saver, which can be used with top drive or rotary table drilling system is housed in a short sub, has a large axial bore for the passage of drilling mud therethrough, a fixed and a movable seal assembly. The movable seal assembly is urged into normally closed position by a stack of Belleville, wave or similar disc stack of springs. The force of the spring stack can be over-ridden by application of sufficient mud pressure from top drive or Kelly to move the moveable seal assembly. Upon application of sufficient mud pressure the movable seal assembly moves downward allowing for flow through the large axial bore. Upon closer of the mud saver a flexible washer associated with fixed seal assembly allows pressure below the mud saver to be relieved to the top of the mud saver, from where return is precluded unless the mud saver is re-opened by application of mud pressure from top drive or Kelly. The short mud saver may be integrated with internal, ball-type blow-out preventer and have a shortened retrievable plug.