投手在连续投出几个快速球后，突然用一记变速球让打者挥棒落空。

After several fastballs, the pitcher surprised the batter with a perfect ___change-up that made him swing too early.

教练在比赛后期突然改变战术，这个变化让对手措手不及。

The coach's unexpected ___change-up in tactics during the late game caught the opponents off guard.