If there is one player I am not (currently) worried about, it's RA. He was lighting up high EVs in ST and the WBC. I don't really care if the talent level wasn't always the same. You aren't doing that if you have declined that much.
It's probably a mechanical issue. And, we've had so few at bats so far, 1 or 2 "off" swings can still have a fairly significant impact on these numbers. Also, it should be noted that his bat speed is STILL in the 84th percentile despite the "decline" we've seen in barely over 2 dozen at bats.