There are three interesting data points that were interesting to Giants fans regarding Buster Posey.
As one of the best strike framers today. Despite playing roughly 4 seasons worth of catching so far, because of that devastating, even worse than NFL nasty hit in 2011, he had 71 Called Strikes Above Average, good for a tie with Mauer for 16th place, covering 1988-2014 (or the last 27 seasons, so a fair amount of history; wish authors would have given us total number of catchers captured in their analysis). And if you look at his catching defensive stats, you will find that resulted in 80.6 runs (or roughly 8-9 wins or roughly 2 wins per season, a huge defensive contribution just from one area).
The stats in his profile don't match what is in the article, but making rough guesses, he is adding around 25 CSAA per season. So in 3 seasons, he would be 9th (depending what Ross does), which would take him up to his 30 YO season. Looking at his stats and those of others still playing at the top of the list, he's one of the best in the past three seasons (except for Lucroy, though Lucroy's 2014 was much reduced versus previous seasons), even better than Yadier and Martin. Good reasons to keep him catching.
But So Does Aging
Looking at the Framing Aging Curve, however, most players his age are headed into a slight decline (and I would bet is a mix of guys who stay as good as they had been and guys either injured - they are catchers after all - or suffered physical declines, which led to the slight decline overall), and then at 30, there is a steep decline in the ability to frame, which suggests that as catchers' physical peak is over and physical decline happens, their ability to frame to gain strikes declines quickly. Doesn't mean he will, but it would mean that he would be defying history of catchers captured in that study.
And this result, especially given the defensive value this provides, some 3-4 wins added (and this is defensive, so the effect is multiplied due to Pythagorean) for the best players, suggests that aging older catchers need to be replaced with younger starters who are good framers as soon as their framing skills decline in their 30's, though some do keep doing well, like Jose Molina.
But age appears to be a powerful factor in decline in the ability to frame (i.e. steal) strikes:
- Jose's brother Yadier hit his decline at age 31, though I would note that he had a poor year at age 26 then reverted back to goodness, and age 31 was last season for him; then again, his FRAA was negative for two consecutive seasons, so this could be it for him defensively.
- McCann hit his decline at age 29, two years going down now.
- Lucroy, who appears to be among the best in his era, had a poor season last year at age 28 (I would note here how Yadier bounced back so perhaps just a glitch).
- AJ Pierzynski was washed up defensively by his 30's, and retroactively, BP has his FRAA as horrible his whole career, so they must have decided their research back then showing him to be good defensively was not correct, making the trade look even more stupid and more likely, in my eyes, that Colletti was the one who instigated that trade, not Sabean.
- Russell Martin didn't have a steep drop but has been gentling getting worse in framing starting at age 29 (which was within career range, but not the last two seasons).
- Mauer has never been a top catcher at framing strikes, but he's been good enough to save about a one win per season, and his decline appears to have started at age 29, which covers the last two seasons.
2015 is Posey's 28 YO season. As I've shown above, all the top catchers above him which has this type of data has shown declines in their ability to frame strikes somewhere in the 29-31 age range. That suggests that his decline in this ability could be starting in the 2016-2018 time frame.
Susac to the Rescue
The authors also analyzed AAA and AA catchers, and guess who popped up on the lists? Susac. He was tied for third with 14 CSAA runs, all the other guys were older than he, and a couple of the guys ahead of him were much older than he was. And he did that catching 56 games in AAA since he spent significant time in the majors (unfortunately, didn't do as well in majors in gaining strikes, in fact, lost a few, though basically at 0). Extrapolate that to Posey's catching, and they were roughly the same on a seasonal basis. Of course, it was only AAA, but he is apparently on his way defensively,
I think that this article makes the case for what I've been suggesting as the way to handle the catching situation over the next few years. We should have Susac spend 2015 working on all his catching defensive abilities, which is his 25 YO season. Then for 2016-2020, the Giants should have Posey and Susac (assuming he can hit well enough at MLB level, something he has shown so far, but will need to prove he can sustain; I believe he can) as co-starters at C and another position on the field. 1B probably works best, but if they can handle 3B, all the better, as then we can keep Belt at 1B.
Posey at one point will decline defensively during this period, and Susac would be wasting his prime strike framing years being a backup, better to trade him and pick up a good veteran than do that, if he's not a starter. By sharing the catching duties, Posey gets less wear and tear, hopefully enabling him to extend his effectiveness in framing pitches as he gets older, while Susac gets quality time at starting catcher (though not full, albeit) and by saving his legs in his youth, perhaps he'll last longer as a good defensive catcher deeper into his 30's. Look at how Jose Molina was able to keep doing well deep into his 30's being a half-time/part-time catcher.