Minecraft wiki entry for Drops, associated text: Common drops may appear at the location of a mob at the moment it receives fatal damage. Most mobs have certain items that they may drop when killed. Some common drops, such as leather, don't always drop, but have a large chance (at least 50%, depending on the drop range) to do so. Some common drops, such as blaze rods, don't drop at all if the mob was not killed by the player.