An added weapon making Aroldis Chapman unhittable

One night, Aroldis Chapman is finishing off hitters with his slider. The next, it’s his 100-plus mph fastball. The two pitches are becoming interchangeable, making the fireballing left-handed closer virtually unhittable. “You think of ‘Chappy,’ you think of the 100-plus mph fastball, but there’s been many a game where his slider has been a really…