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Myth of the 'sophomore slump' among Rookie of the Year winners

In 2014 two unlikely rookies emerged onto the baseball scene to win each league’s respective Rookie of the Year Award. What does history show us about the RoY and a 'sophomore slump'

Dale Zanine-USA TODAY Sports

Prior to his arrival, Jose Abreu was a man of mystery who tore up Serie Nacional league in Cuba before defecting to the United States in August 2013. The numbers from the Cuban league speak for themselves, as Abreu hit for plus plus power and plus plus average, but the bar had been set high with the rapid ascent to stardom for Yoenis Cespedes and Yasiel Puig. Like his fellow countrymen, Abreu adjusted to a new country, a new culture, and in many ways a new game to quickly become a household name within the Major League Baseball community (a profile of Abreu's journey from Cuba to the U.S. is chronicled here by Michael E. Miller; I highly recommend it).

In the National League, Jacob deGrom defied scouting expectations to claim the N.L. Rookie of the Year award. He started playing college ball as a shortstop but eventually becoming Stetson College's number one starter. After signing with the Mets as a ninth round pick, he had Tommy John Surgery, and was projected as a fourth starter in a best-case scenario but was thrust into the Mets rotation due to performance and the Mets lack of depth.

There tends to be a narrative around second year players regarding a ‘sophomore slump', and while such a regression may exist in the aggregate, the results are mixed (at best) when specifically analyzing the second year performance of Rookies of the Year.

Over the past ten seasons, the RoY second-year results do not show a clear pattern of the regression. It seems logical that rookies won the award because they were excelling for a short period of time and that such sustained success would not be likely over the course of the next year as well. Additionally, with the generic narrative of a ‘sophomore slump' I thought for sure that the data would yield more examples of players faltering after winning the award.

Year (League) Player Position Rookie PAs Soph PAs Rookie Average Soph Avg Rookie OBP Soph OBP Rookie SLG Soph SLG Rookie HR Soph HR Rookie wRC+ Soph wRC+ Delta wRC+
2014 (AL) Jose Abreu 1B/DH 556 --- .317 --- .383 --- .581 --- 36 --- 165 --- ---
2013 (AL) Wil Myers OF 373 361 .293 .222 .354 .294 .478 .32 13 6 131 78 -53
2012 (AL) Mike Trout OF 639 716 .326 .323 .399 .432 .564 .557 30 27 167 176 9
2012 (NL) Bryce Harper OF 597 497 .27 .274 .34 .274 .477 .486 22 20 121 137 16
2010 (NL) Buster Posey* C 443 185 .305 .284 .357 .368 .505 .389 18 4 134 116 -18
2009 (NL) Chris Coghlan OF 565 400 .321 .268 .39 .335 .46 .383 9 5 127 94 -33
2008 (AL) Evan Longoria 3B 508 671 .272 .281 .343 .364 .531 .526 27 33 128 132 4
2008 (NL) Geovany Soto C 563 389 .285 .218 .364 .321 .504 .381 23 11 120 81 -39
2007 (AL) Dustin Pedroia 2B 581 726 .317 .326 .376 .371 .442 .493 8 17 117 127 10
2007 (NL) Ryan Braun OF 492 663 .324 .285 .37 .335 .634 .553 34 37 155 129 -26
2006 (NL) Hanley Ramirez SS 700 706 .292 .332 .353 .386 .48 .562 17 29 116 144 28
2005 (NL) Ryan Howard 1B 348 704 .288 .313 .356 .425 .567 .659 22 58 132 162 30

*Player Injured in Second Season

On the positional player side, Ryan Howard and Hanley Ramirez used their Rookie of the Year campaigns as a prelude to greater things at the plate. Howard followed up a 22-home run campaign in only 348 plate appearances with a full season's worth of 58 home runs the following year. The following season (2006), Hanley Ramirez won the award with a 116 wRC+, that he crushed in 2007 with a 144 campaign. Not all positional players were as successful in their RoY postlude.

Of the eleven positional players to win the award, four took a significant step back. Ryan Braun put up an unworldly 155 wRC+ his 113 game rookie campaign, supported by a .361 batting average on batted balls. When that number stabilized to league average the following year, his wRC+ was ‘only' 129.

Geovany Soto, Chris Coghlan, and Wil Myers took significant steps back at the plate, as Soto's home run total dwindled from 23 to 11, Coghlan's average and on-base percentage took a major dive, and Wil Myers' power and average significantly declined.

Evan Longoria's numbers at the plate were mostly the same in his sophomore season, as were Dustin Pedroia's and Mike Trout's. Each improved marginally at the dish and would not be described as having suffered from a sophomore slump.

What does this tell us about Jose Abreu? As expected, Abreu really only contributes at the plate, as he is a slow slugger who can hit for average, but provides little value in the field or on the base paths. He played in 145 games last season and ended the year hitting 65% above league average. In his second year in Major League Baseball, he is entering his age-28 season, at which time a player is not exactly in his prime, but before talent declines at an increasing rate and the player is downgraded substantially based on age.

Both FanGraphs' Steamer and ZiPS projection systems show a bit of a step back from a five-win player to a four-win player. Nevertheless, it would be surprising if Abreu does not have another year where he hits 30+ home runs and a .290-.300 average.

Last year, Abreu adjusted well to the MLB strike zone. His 8.2% walk rate was higher than league average, as was his 21.1% strikeout rate. The strikeout rate is less concerning because of the power output. One place where Abreu will likely regress is in his batting average on balls in play. His .356 BABIP is likely to fall, but due to his hitter profile, and the fact that he was 37th in hard-hit average in 2014, he could potentially sustain a BABIP in the .300-.320 range. I think it's likely Abreu's wRC+ declines a bit, but would be surprised if it's more than 5-10% different than last year, which I would not consider a ‘sophomore slump'.

Year (League) Player Position Rookie Innings Soph Innings Rookie ERA Soph ERA Rookie FIP Soph FIP Rookie K/9 Soph K K/9 Rookie BB/9 Soph BB/9 Rookie ERA- Soph ERA- Delta ERA-
2014 (NL) Jacob deGrom SP 140 --- 2.69 --- 2.67 --- 9.24 --- 2.76 --- 78 --- ---
2013 (NL) Jose Fernandez* SP 172.2 51.2 2.19 2.44 2.73 2.18 9.75 12.19 3.02 2.26 58 66 -8
2011 (NL) Craig Kimbrel RP 77 62.2 2.1 1.01 1.52 0.78 14.84 16.66 3.74 2.01 56 26 30
2011 (AL) Jeremy Hellickson SP 189 177 2.95 3.1 4.44 4.6 5.57 6.31 3.43 3 76 80 -4
2010 (AL) Neftali Feliz RP 69.1 62.1 2.73 2.74 2.96 3.57 9.22 7.8 2.34 4.33 61 63 -2
2009 (AL) Andrew Bailey* RP 83.1 49 1.84 1.47 2.56 2.96 9.83 7.71 2.59 2.39 43 36 7
2006 (AL) Justin Verlander SP 186 201.2 3.63 3.66 4.35 3.99 6 8.17 2.9 2.99 80 80
2005 (AL) Huston Street RP 78.1 70.2 1.72 3.31 2.75 2.62 8.27 8.53 2.99 1.66 41 74 -33

*Player Injured in Second Season

On the pitching side, the results are similarly muddled. Craig Kimbrel excelled in his second season posting up an ERA- 30 points better than his rookie season — a stark contrast to Huston Street, whose ERA- was 30 points worse.

Starters have likewise shown mixed results, as Justin Verlander was consistent from his first to second year, as was Jeremy Hellickson.

Of particular note, of the seven previous pitchers who have won the Rookie of the Year Awards since 2005, only Justin Verlander has increased his innings in his second year. It's a small sample, but it still demonstrates the volatility of a pitcher. Jose Fernandez and Andrew Bailey both succumbed to Tommy John Surgery the year after their excellent rookie seasons.

The Mets would be happy if a healthy Jacob deGrom gave them 180 innings in 2015, especially considering Zach Wheeler's injury. Justin Verlander and Jeremy Hellickson were consistent in their second season, but unlike Hellickson (and more like Verlander, a good sign), deGrom's ERA and FIP mirrored one another, so there does not seem to be concern for ERA regression.

With a strikeout per nine higher than Verlander and a walk per nine lower, the Mets should continue to expect excellent performance from deGrom. Both Steamer and ZiPS project an increase in ERA (by 1.08 and .71 runs respectively) but with 77.4% strand rate, a sustainable .297 BABIP, and a 3.03 xFIP there's little reason to think deGrom will experience a significant step back in his performance.

Neither Abreu nor deGrom strike me as a prime candidate for a ‘sophomore slump', and the history of Rookie of the Year award winners do not indicate a pattern. The White Sox and Mets are both hoping each stay healthy and take a step forward, but even if both players produce similarly to 2014, they will remain at an all-star level.

Statistics courtesy of Fangraphs

Steven Martano is a Featured Writer at Beyond the Box Score. You can follow him on Twitter at @SMartano.