Jeff did a number of year 1/year 2 queries that look at the greatest improvements from one year to the next. This can be misleading in terms of a breakout season because the player could just as easily have had an off-year or an injury year prior to his "breakout" and create the illusion of a major jump in performance.
So here we are looking at the greatest jumps in wRC+ from a player's breakout year to his previous high. I used the same 300 PA requirement used in the article for both seasons.
Harper falls to 29th on the list of greatest breakouts by this method, comparing his 197 wRC+ in 2015 season with his previous high of 137 in 2013 nets him a jump of 60 points, not quite as high as the top ten:
All time Breakouts
|#||Name||Age||Season||wRC+||PA||previos high wRC+||JUMP||previous high season||previous high PA||Years since previous high||Years since breakout|
Devin Mesoraco's showing inside the top ten is surprising to me, perhaps he's been forgotten about already since a dismal injury-plagued follow-up in 2015.
Al Kaline jumps from fifth in the article to number one here, but with just two full seasons before his breakout year.
Other recent notables include Jose Bautista's 2010 breakout at #19, Justin Turner and Brandon Moss at #26 and Alex Avila's standout 2010 tied with Harper.
And personal favorite John Lowenstein broke out in his 12th year as a major leaguer to hit for a 173 wRC+ 65 points higher than his next best performance previously. He was 35 years old.
Here is the top 100: https://docs.google.com/spreadsheets/d/1iF8gb76VmxzXUUjLIBs8dbkzWlVn1vSlknrkJOQCees/edit?usp=sharing
Here is a picture of a face, parts of it belonging to the author, parts to John Lowenstein: