The introduction of the designated hitter drastically alters one aspect of baseball – the pinch-hitter or cold bat off the bench. A special talent is needed to pinch-hit and some have made a career out of that one specific ability.
The National League certainly has a need since they had pitchers hit for a league average of just .135 in 2016. That appears to be the capabilities season after season. In comparison, American League pitchers managed to hit .100 in 2016.
In 2016, the American League hit .196 off the bench in 1428 plate appearances, according to Fangraphs, from which all the following data was extracted.