I was looking for it and maybe @Luke-OH can refresh us but he said something like he made swing changes and with the juiced ball - his warning track fly outs are now reaching the seats. Obviously there is more to it than that but it will be interesting to see how he fares next year, wherever he plays.
Here is Drungo's seat of the pants analysis and some stats from that same thread (p 86):
"You don't kick yourself for not recognizing wildly out of character things that might happen in the future. Did the Red Sox kick themselves for missing out on Brady's 50 homer season? Do the Orioles kick themselves for not recognizing that Jose Bautista would go crazy six years after he was a Rule 5er?
Last year Yastrzemski spent a month OPSing .603 in AA at the age of 27. The Giants picked him up because they were all out of outfielders so why not? Just as the O's did with Dwight Smith Jr. Nobody had a crystal ball, I doubt anyone saw the year of the superball coming."
"Yaz is already in the top 20 homer seasons of all time by old (27+) rookies. That list is about 75% players who were stuck in Cuba, Japan, the Negro Leagues, or the old independent high minors prior to the draft era. Plus a few players like Josh Willingham, Christian Walker, Justin Bour, Garrett Jones, Brian Daubach. As far as I can tell everyone except Yaz on the list had a history of hitting for power wherever they were prior to their rookie breakout."