I think they focused on hitters because in general a lot more attention is already paid to fatigue with pitchers (carefully monitoring innings pitched, pitch co

I think they focused on hitters because in general a lot more attention is already paid to fatigue with pitchers (carefully monitoring innings pitched, pitch counts, rest days, and so on). It's possible (although not guaranteed) that there is much more room for improvement in the way teams deal with fatigue for hitters.