Ronald Acuna Is Already Setting Records by Improving at Every Level

There have been several surprising prospect performances this year, but the one that seems to top the rest has been Atlanta Braves outfielder Ronald Acuna. The 19-year-old began his season in high-A and, by my notes, was unranked in the MLB pipeline top-100 (he was 36^th on Keith Law’s list and 67^th on Baseball America).

Fast forward to now, and Acuna has been promoted twice and is a consensus top-10 prospect. In the recent prospect hot sheet chat, Baseball America’s Josh Norris speculated that Acuna was a frontrunner for minor league player of the year and next season’s #1 prospect overall.

The aspect that I could not get my head around is that Acuna is improving faster than he can be promoted. With at least 100 PA at each level, he has improved every relevant rate stat with each stop.

Name	Team	Age	G	AB	PA	HR	AVG	BB%	K%	OBP	SLG	OPS	ISO	wRC	wRC_plus
Ronald Acuna	Braves (A+)	19	28	115	126	3	0.287	6.30%	31.70%	0.336	0.478	0.814	0.191	18	135
Ronald Acuna	Braves (AA)	19	57	221	243	9	0.326	7.40%	23.00%	0.374	0.52	0.895	0.195	41	159
Ronald Acuna	Braves (AAA)	19	24	92	107	4	0.348	12.10%	18.70%	0.434	0.576	1.01	0.228	22	183

This led me to answer the question of whether this had ever been observed before.

I pulled every minor league player season from 2006-2017 (the farthest back FanGraphs can go). I filtered on at least 100 PA, and consolidated a list where players appeared in at least three levels. I used wRC+ as a catchall stat for offensive production and scored players that improved their output in the jump from one level to the next.

It is worth observing that this list is quite artificial — not many players appear in three different minor league teams in a single season, and only 22 have done so in the past 11 years. And the list certainly isn’t a who’s-who of top prospects, so take this analysis with a grain of salt.

Since 2006, Acuna is the only minor-league player to have posted improved wRC+ at three different stops in the same season (see chart below, labeled players with blue lines showed improvement in at least one jump). While Acuna’s high-A 135 wRC+ wasn’t setting the world on fire, posting a 183 wRC+ at his third league level in a single season is untouchable.

See graph

Owing to Acuna’s excellent hit tool, he is also the only prospect to have posted similar improvements in AVG, OBP or OPS since 2006.

On plate-discipline statistics, the only other player to show the consistent improvement in BB% is Ryan Court (2013). Two other players show a consistent decline in K% across each level (Brett Wallace and Sawyer Carroll in 2009).

For power statistics, Acuna also finds a little company. Two other players showed improvements in isolated power at each level, Tyler Pastornicky in 2015 and Rando Moreno in 2016, though their improvements went from horrific (0.038 and 0.040, respectively) to simply not good (0.111 and 0.082). Pastornicky was the only non-Acuna player to increase his SLG at each level (.314 to .394 compared to Acuna’s .478 to .576).

As was said at the outset, the players that reach 100 PA in three levels in a single season are not any sort of elite bunch. But it is telling that among them, Acuna is the only one that has shown a consistent ability to improve while facing better and older talent. I’m not holding my breath for a 200 wRC+ when Acuna makes it to The Show, but I will be watching.