Season's nearing an end, time for an update on what we have in-house at third.
Riley has done very well in 194 AA plate appearances. But dig a little deeper and we see a BABIP of .374 (he was at .289 at high A). This effectively masked a spike in his strikeout rate to 25.3% in AA from 21.8 in high A. Also worthy of consideration is that the sample at High A consisted of 339 plate appearances and should probably be given more weight than the significantly smaller sample in AA.
Ruiz hit better in AAA after his demotion. But as with Riley if you just emphasize his hot streaks and ignore his struggles, you aren't going to get as good a picture as if you take the entire sample into account. And that sample shows a AAA slash line this year of .247/.322/.446. Relative to last year, when he was also in AAA, the strikeout rate was up, the walk rate was down, but the ISO showed a nice increase.
I don't think either Ruiz or Riley projects as a major league regular. But there is still a plausible scenario out there where they form an effective platoon.
I also want to touch on Johan Camargo, who has had a very nice season both in AAA and the majors. As is often the case, the most informative number is his BABIP, which was .340 in AAA and .364 in the majors. The .364 in the majors masked a problematic strikeout rate (21.8%).
The most intriguing thing about Camargo are indications that the power is starting to develop. His ISO numbers both in AAA and the majors were up significantly from prior seasons. I can see a scenario where the strikeout rate drops below 20%, the ISO improvement is sustained and the BABIP stabilizes at about .320. Couple that with strong defense and your would have an acceptable everyday major league third baseman. However, I put the odds of that kind of scenario at 30-40%.
To me Camargo has a better chance than Riley or Ruiz of developing into a solid everyday player, but the odds are still less than 50%. However, the three of them collectively have enough promise that I'd be inclined not to invest in an everyday third baseman this off-season. I'd let the internal options play out for at least the first half of 2018.