Ronald Acuna is Baseball America's No. 1 prospect. You knew that already. He'll be playing for the big-league Braves soon – maybe on opening day, surely by Memorial Day. I've seen him do more than take batting practice. He's really good.
He’s also 20. He began last season in Single-A. This time a year ago, he was Baseball America’s No. 67 prospect. That in mind, it seems prudent to ask: In a sport famously difficult to predict, what’s a reasonable rookie season for the talented Mr. Acuna?
Here's the projection from Dan Szymborski's ZiPS – 594 plate appearances, 21 homers, 73 RBIs, 33 stolen bases; .269 batting average, .321 on-base percentage, .452 slugging percentage; a zWAR (Szymborski's version of wins above replacement) of 2.8.
Here’s the projection from Baseball Prospectus’ PECOTA – 537 plate appearances, 20 homers, 67 RBIs, 26 stolen bases; slash line of .268/.320/.450; a WARP (BP’s version) of 0.9.
Caveats: There’s no guarantee Acuna will have 500 plate appearances in the majors this season; we don’t know where he’ll start the season, if he’ll play full-time when he arrives or if he’ll stay healthy. Note, though, that the ZiPS and PECOTA slash lines are almost identical, with the counting numbers (homers, RBIs, SBs) so close that the 47 more PAs afforded by ZiPs come close to constituting the difference. The variance between WARs could be ascribed to methodology.
The key point is that two leading statistical projections see Acuna having what would be a fine rookie season. How fine? Here’s a look at how outfielders ranked among Baseball America’s overall top five prospects over the past 10 years fared in their first full big-league seasons. (In some cases, those first full seasons weren’t technically rookie years.)
Colby Rasmus, Cardinals: No. 5 prospect in 2008, No. 3 in 2009; in 2009, had 16 home runs, 52 RBIs and three stolen bases; slash line of .251/.352/.407; Baseball-Reference WAR of 1.9; eighth in rookie of the year voting.
Jason Heyward, Braves: No. 5 prospect in 2009, No. 1 in 2010; in 2010, had 18 homers, 72 RBIs and 11 stolen bases; slash line of .277/.393/.456; 6.4 WAR; All-Star; second in ROY voting, 20th in MVP voting.
Giancarlo Stanton, Marlins: No. 3 prospect in 2010; had 22 homers, 59 RBIs and five stolen bases as a rookie; slash line of .259/.326/.507; 2.8 WAR.
Bryce Harper, Nationals: No. 1 prospect in 2011 and 2012; in 2012, had 22 homers, 59 RBIs and 18 steals; slash line of 270/.340/.477; 5.1 WAR; All-Star; Rookie of the Year, 30th in MVP voting.
Mike Trout, Angels: No. 2 prospect in 2011, No. 3 in 2012; played 40 MLB games in 2011; in 2012, had 30 homers, 83 RBIs and 49 stolen bases; slash line of .326/.399/.564; 8.6 WAR; All-Star; Rookie of the Year, second in MVP voting.
Domonic Brown, Phillies: No. 4 prospect in 2011; played 35 MLB games in 2010, 56 each in 2011 and 2012; in 2013, his first full season, had 27 homers, 83 RBIs and eight stolen bases; slash line of .272/.324/.484; 2.5 WAR; All-Star.
Oscar Taveras, Cardinals: No. 3 prospect in 2013 and 2014; played 80 MLB games in 2014; had three homers and 22 RBIs; slash line .239/.278/.312; minus-1.4 WAR.
Wil Myers, Rays: No. 4 prospect in 2013; in 88 games, had 13 homers, 53 RBIs and five stolen bases; slash line of .293/.354/.478; 1.9 WAR; Rookie of the Year.
Byron Buxton, Twins: No. 1 prospect in 2014, No. 2 in 2015 and 2016; played 46 MLB games in 2015, 92 in 2016; in 2017, his first full big-league season, had 16 homers, 51 RBIs and 29 stolen bases; slash line of .253/.314/.413; 5.1 WAR; won Gold Glove, 18th in MVP voting.
Andrew Benintendi, Red Sox: No. 1 prospect in 2017; played 34 MLB games in 2016; in 2017, had 20 homers, 90 RBIs and 20 stolen bases; slash line of.271/.352/.424; 2.6 WAR; second in ROY voting.
Trout, Harper and Stanton have won MVP awards. Heyward has had four seasons of a 5.8 WAR or better, none since signing with the Cubs. Buxton is the outfield mainstay of a Minnesota team that just went from 103 losses to a wild card. Myers is a solid but not spectacular big-league hitter. Benintendi has made a bright start.
Rasmus has become a nomad; he just signed a minor-league contract with Baltimore, his fifth organization. Brown hasn’t played in the majors since 2015 and was released by Colorado last summer. Taveras was killed in a car crash in October 2014.
If we go by projected slash lines and counting numbers, an Acuna rookie season wouldn’t be far off Heyward’s – a lesser OBP, but more homers and stolen bases. (A goodly chunk of Heyward’s WAR, as we know, has come from defense and base running, and it’s tough to predict those.) That’s pretty fast company.
Realistically, we shouldn’t expect Acuna to be the next Trout, who’s an entity unto himself. Or should we? This was the aforementioned Szymborski in a post for ESPN Insider:
"ZiPS is projecting (Acuna's) career WAR at 14 wins more than the second-place (rookie) ... ZiPS has projected only three rookies to get over the 50 WAR barrier: Mike Trout, Kris Bryant and Acuna."
So there you go. That’s the first comparison by a respected stat maven to include both the best player of his generation and a 20-year-old Braves prospect. Feel free to clip and save. (Or, this being 2018, take a screenshot.)
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