We don't have a ton of evidence to go on, but there are a few interesting early trends in how Ryan Hanigan and Devin Mesoraco are being used. Hanigan we know pretty well at this point, while Mesoraco's skills in the major league level are still emerging.
Devin had been the better hitting catcher until recently, though not by a margin that couldn't be more than made up by Hanigan's expertise and defense behind the plate.
Here's how they stand after yesteday's game:
Both Mesoraco and Hanigan have crushed lefties this season (in limited exposure) and have a history of doing so. Hanigan's MLB line against lefties is over 100 OPS points above his righty splits: .278/.394/.424.
The playing time breakdown makes good sense so far. Mesoraco shouldn't ride bench more than 3 days at a time, especially since there are some nights when the Reds might need more pop in their lineup than game-calling skill. Still, we shouldn't underestimate how Hanigan has honed his craft. At this point, he has a very clear advantage in working with the staff, gunning down runners and framing pitches.
Mesoraco has looked good, to my eye, in the pitch-blocking department. While the defensive indicators are negative for him in his early MLB career, we can probably throw them out entirely. At worst, he's setting the floor for his big league career.
Here's the percentage of batters faced by catcher for each member of the starting rotation:
Hanigan has been the personal catcher for the two longest-tenured pitchers in the Reds rotation (by major league service time with the Reds). Among the three starters Mesoraco has caught this season, Leake and Bailey both have better ERA splits with him than RyHan. I would put almost no stock in that at all, especially since Hanigan's work with both has been so limited.
However, Latos has been drastically better with Hanigan and there may be something to that, even if "catcher ERA" is a crude and usually worthless statistic. I would guess we're going to see more of those two together, assuming Dusty is basing his decisions heavily on battery rapport and experience.
Leake might benefit from Hanigan's game-calling expertise, but Devin needs to start and continue to learn on the job (I would argue, at least 40% of the time).
Depending on how the schedule and other factors shake out, Mesoraco could take the remainder of Leake's time, with Hanigan pairing with Latos the rest of the way. That would work out to a roughly 60/40 split.
Anything more skewed more toward Hanigan would give short shrift to Mesoraco, but I'd be OK with that for Year One.