It is used by persons who watch the sport ‘baseball’.  It is used when a runner clearly does not reach the base before the ball arrives.

他還差得遠呢！

本句源自棒球觀眾的說法，意思是，大家都看得一清二楚，當跑壘者還沒抵達壘包前，球早已傳到該壘了。