The crew reported to work without one crewmember. The rig supervisor assisted the crew in making a connection. After they completed the connection, they removed the slips from the rotary bushings. One of the crewmembers placed the lead tongs against the A-Frame with a small securing chain. The rig supervisor engaged the # 1 Mud Pump clutch. While watching the pump pressure gauge, he reached up and engaged what he presumed was the # 1 mud pump throttle. Instead, he engaged the clutch to the breakout line on the lead tongs. This forced the tongs to move from their secured position towards the drawworks. They struck the employee and pinned him against the drawworks. The employee suffered five broken ribs, a punctured left lung, several abrasions and a bruised left arm.