Sano could probably put up numbers similar to Arcia this year if he went north out of spring training - low avg, lots of Ks, plenty of power, questionable defence. If there wasn't a solid 3B option ahead of him I'd say bring him up and let him learn on the job. Plouffe is a solid option though, and there's no harm in giving Sano a couple of months in AAA to get the rust off that surgically repaired elbow, get some confidence he can make all the plays he needs to from hot corner and blow away AAA pitching before bringing him up, hopefully for good. It may sound counter-intuitive given Buxton has barely hit a ball above A+, but I would have more confidence in him contributing from the get go, if only with the glove and on the base paths in the first instance before his bat catches up (which I'm sure it would). TBH though I don't see either of them breaking camp with the MLB club. If I was betting, I'd guess we'll see Sano at end May/early June and Buxton after the All Star break.