Washington's Juan Soto led all NL rookies qualifying for the batting title in on-base percentage, OPS and walk rate despite starting the season with Hagerstown (Class A). (John McDonnell/The Washington Post)

This year’s National League rookie of the year race is a good one. Ronald Acuna Jr., the hot-hitting outfielder for the Atlanta Braves, and Juan Soto, the Washington Nationals' 19-year-old phenom, are expected to be at the top of nearly every voter’s ballot.

Acuna, who hit .293 with 26 home runs and a .917 on-base-plus-slugging percentage (OPS), caught fire after Manager Brian Snitker moved him into the leadoff spot after July’s All-Star Game. He hit .328 with a 1.042 OPS from the top spot, and his eight leadoff home runs are a franchise record. Acuna also joined Mike Trout as the only players to hit at least 25 home runs and steal 15 bases in their rookie season. Overall, his sensational campaign was worth 3.7 wins above what a replacement-level player would provide.


Ronald Acuna Jr. spray chart for 2018.

Soto led all NL rookies qualifying for the batting title in on-base percentage (.406), OPS (0.923) and walk rate (16 percent) despite starting the season with Class A Hagerstown. He joined Mel Ott (1928) and Tony Conigliaro (1964) as the only teenagers to have a slugging percentage over .500, and Soto is the only one to ever maintain an on-base percentage of .400 or higher. He, too, was worth 3.7 wins above replacement.


Juan Soto's swing rate in 2018.

Not only were their overall values the same, the slash lines for each were nearly identical, with Acuna showcasing more power and Soto exhibiting better plate discipline.

Player PA AVG OBP SLG OPS fWAR
Ronald Acuna, Braves 487 .293 .366 .552 .917 3.7
Juan Soto, Nationals 494 .292 .406 .517 .923 3.7

But according to the final survey of MLB.com’s members of Baseball Writers' Association of America, Acuna appears to be the runaway winner with 34 of 36 first-place votes, likely the result of two factors: defense and team success.

Per FanGraphs, Acuna saved four runs with his glove, 14th most among NL outfielders this season. Soto, by comparison, cost the Nationals five runs due to his fielding. And Acuna flashed his glove for the NL East winner, helping send his team to the playoffs, whereas Soto patrolled left field for a disappointing, non-playoff team.

One could still argue Soto did more to help his team than did Acuna. For example, a metric known as win probability added, which uses Tom Tango’s win expectancy charts to measure how much a player contributes to his team’s chances of winning a game, shows Soto (3.1 WPA) was significantly more valuable than Acuna (1.7) in 2018. If we adjust that for leverage, which is a measure of how important a game situation is, the gap narrows but still leaves Soto with a commanding lead.


Which NL rookie was most valuable in 2018? Win probability added (WPA) credits or debits the player based on how much their action increased their team’s odds of winning. Context-neutral wins (WPA/LI) shows how much value a player provided regardless of the situation he was put in.

Deride advanced metrics if you want, but both of last year’s winners, Cody Bellinger in the NL and Aaron Judge in the AL, led all rookies in their respective leagues for context-neutral wins. Same for Corey Seager and Michael Fulmer in 2016 and Kris Bryant and Carlos Correa in 2015. Include pitcher Jose Fernandez in 2013 and the eventual NL rookie of the year winner led the league in context-neutral wins every year since 2012 with the exception of one, Jacob deGrom in 2014, who finished second behind Ken Giles that season.

Will this be enough to sway other voters to put their support behind Soto rather than Acuna? Probably not, but in a race this close, the tie should go to whoever helped his team the most, regardless of whether that team was in a pennant chase.

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