I admit I don't know the detailed physical status of Kirk, but this Tapia thing isn't just about resting Springer, it's something else. Kirk has also been benched on multiple occasions for guys like Collins, not just resting the starters. He was also benched quite a bit last year as well, including getting pinch hit for by Danny Valera.
I get that he's a big fat guy, but if a 23 year old kid can't DH on back to back days that's borderline disabled. Benjie Molina played catcher into his late 30s.
Tapia DHing against a LHP was the clearest sign I could find that they're intentionally finding him ABs. All the guys they were supposedly resting ended up playing half the game anyways.
The front office gets tunnel vision on profiles that they like (Morales, Grichuk, Tapia). I'm sure the FO will pat themselves on the back when Tapia reaches his .690 OPS ceiling but that still really sucks.