retrieve the ball, look the runner back to third. if he is too far off then the 3rd baseman should raise his arms signaling that the catcher should throw to third. Assuming the 3rd baseman does not raise his arm the catcher should take 2-3 strides towards the pitchers mound creating a "lane" to throw. The firstbaseman should be on the "inside" part of the base and the catcher needs to make a crisp throw to first so the guy on third doesnt score on the throw.