Statistics like this are only partially helpful. How often did Hendricks pitch against the other team's #1? If often, his 18 wins is impressive, if hardly ever, not so much. If X pitches 10X against Cole, Verlander, and Strasberg is 2 and 7 that bad? You get the idea.
I certainly get the idea.
However, I am not aware of any single stat that is more than partially helpful.
And as a practical matter, after the first week of the season, and certainly after the first rain out, it is very difficult for any manager to match his best pitcher against other teams best pitcher. Rotations seldom match up that perfectly, and very few managers would move back his ace more than perhaps a single game, and certainly would not move him up to three days rest to achieve such a match.
But even if teams were to achieve a perfect match, it still seems helpful to know if your # 5 starter is performing better or worse than the rest of the league's # 5 starter.