The 2015 Rookie Class Was the Best in 100 Years

Toward the end of July, something had become apparent in the 2015 season: it was an unquestionably great year for talented positional rookies. That was easy to see by the first half introduction of All-Star caliber players in Kris Bryant, Carlos Correa, and Joc Pederson. Many others added to the top-heavy, strong class. As it turns out, that excellence was also borne out in the data: the first half of the 2015 season had the most rookies with 1.0+ WAR and the most combined rookie WAR since 2005.

Digging a little deeper, it turned out that only two seasons in the last 40 years compared to the playing-time adjusted WAR the 2015 rookies put up in the first half. Take a look at this interactive chart that compares the first half of this past season with those from the past 40 years:

Rookies also accounted for a greater share of playing time in the first half of this season than in any first half of a season during the past 40 years. Again, an interactive chart from the original piece to illustrate that point:

After sorting through that data, now we know for certain : the first half of 2015 was historically great for first-year players. There are a lot of reasons behind that — reasons that were discussed in the comments section of the original piece and are outside the scope of this particular article. That needs — in fact, deserves — its own piece on a future day. Naturally, the question now becomes how the 2015 rookies fared for the rest of the season. And here we are. Now, with a full season in the books, we can take full-season data from years past and compare it to 2015.

The other good news? Our leaderboards only had first-half splits going back to 1974, and we obviously have full season stats going back much further than that — meaning we can look at a much large sample in this piece. Let’s start with the percent of total MLB plate appearances by rookies since the start of the live-ball era (1920) and compare it to this year. All charts in this piece are interactive, so feel free to hover over bars to see exact years/data:

We can see that the share of rookie plate appearances for 2015 was the highest since 1982, but can’t touch the wartime levels of the mid-1940s or the 1969 expansion of the league. World War II caused a slight variation in roster sizes, which is also something we should keep in mind when looking at these figures. Nevertheless, the highest share of rookie plate appearances in the last 30-plus years is still an impressive mark for 2015, and shows just how much of an influence rookies had on the league this year.

What was that influence, production-wise? Let’s bring in our WAR values for our time period. Because plate appearances can vary so greatly between years for rookies (for instance, 1956 had only 13,195 PAs by rookies; 1999 had 28,373), I’ve adjusted the WAR each rookie class produced, modifying it to assume 600 plate appearances:

There’s no other way to put it: this is remarkable. No other year even comes close to 2015, with 1987 and 2007 being the only years in remote proximity based on WAR/600. The 1987 season featured Mark McGwire (5.1 WAR), Kevin Seitzer (5.1), Devon White (4.6) and Mike Greenwell (3.4) among its most notable rookies, while 2007 offered Troy Tulowitzki (5.2 WAR), Dustin Pedroia (3.7), Hunter Pence (3.5), and Ryan Braun (2.5). Those were amazing rookie classes. And yet 2015 blows them away.

After the incredible showing from the 2015 rookies in the first half of the season, I expected the league to catch up a little, and for the rookies not to produce at quite the same level during the second half of the season. That can really only be said of a few players (Joc Pederson comes to mind, who put up 3.1 WAR in the first half before dropping -0.3 WAR in the second) — and for each instance of one of those players who declined, there was another rookie who took the league by storm.

There was Francisco Lindor, who produced 4.5 WAR in the second half after his late call up; Odubel Herrera produced 3.7; Kris Bryant was good for 3.1; Jung-ho Kang put up 2.5. There were 19 rookies who produced at least +1.0 WAR in the second half of 2015, an increase from 17 in the first half. This year’s rookies not only replicated their incredible and historic first half production in the second half; they actually exceeded it.

There’s one figure that best underlines that point. In the first half, the top 20 rookies produced a combined 29.9 WAR, the highest mark in at least the past 40 years; the top 20 rookies during the second half produced a whopping combined 37.5 WAR. In other words, at the All-Star break, we thought that 2015 might be the best year we’d ever seen for rookies. It turns out it was even better than we thought.

The 2015 season offered a perfect storm in the movement toward bringing the most talented rookies up sooner: they are cheaper than veteran players, ready to be as good as average major leaguers at increasingly younger ages, and can learn the polish they need while on the job in the big leagues. After looking at this data, it’s not at all crazy to think that the structure of MLB’s current arbitration system — which keeps rookies down in the minors for longer than they would be otherwise — is ripe for reform. If that turns out to be the case, we might not have seen the best rookie class yet.



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Owen Watson writes for FanGraphs and The Hardball Times. Follow him on Twitter @ohwatson.


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Phillies113
Member
Member
6 months 13 days ago

So…baseball is dying, right?

durn
Guest
durn
6 months 13 days ago

No, just the fans are.

Kevin
Guest
Kevin
6 months 13 days ago

Could this be a contributing factor to the wild deviations in MLB projections these last few years? Influx of young talent, whom are more difficult to project due to their lack of a major league track record, leading to more unexpected results?

Ben
Guest
Ben
6 months 13 days ago

You should ask that question during the next Dan S. chat. I’d be interested in his take…

Ryan
Guest
Ryan
6 months 13 days ago

Wouldn’t the fact that all these players came up, many before it was expected, indicate that the current arbitration system in fact doesn’t discourage bringing the players up as much as we thought? I think this year was very encouraging on that front.

Angela Merkel's boner
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Angela Merkel's boner
6 months 13 days ago

Thanks for the fine article, Owen! What an exciting time for fans of all stripes.

Marco
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Marco
6 months 13 days ago

Let’s all just take one more moment to ponder Lindor putting up 4.5 WAR [b]in the second half of the season. [/b]

Ok, we good? Good. Carry on.

Francisco Lindore
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Francisco Lindore
6 months 13 days ago

440 PA on the season, people act like I played 1/2 a year.

Kershawshank Redemption
Guest
Kershawshank Redemption
6 months 13 days ago

True enough..

The 54 wRC+ with below average base running in 111 first half PA compared to the 154 wRC+ with average base running in 327 second half PA mean that this statement is still close to being true..

Ben
Guest
Ben
6 months 13 days ago

Good read, but an article about standout rookies just has to include Matt Duffy’s name.

Merv Throneberry
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Merv Throneberry
6 months 13 days ago

Miguel Sano!

Keith Hernandez's Moustache
Guest
Keith Hernandez's Moustache
6 months 13 days ago

Michael Conforto’s 2.1 WAR in 194 ABs!

francis
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francis
6 months 13 days ago

Re Conforto, not enough PAs. I’d say you need at least 400PAs to show enough staying power to get a mention. Look at Joc. It’s not even clear if he’s a starter at this point.

He hit .178 with a OBP/SLG/OPS of .317/.300/.617 in the 2nd half.

francis
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francis
6 months 13 days ago

Low PAs also keeps Franco and Schwarber off of the standouts list.

mettle
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mettle
6 months 13 days ago

In a way, this is to be expected: Any pool of players where there is selection pressure will gravitate towards being better in light of your selection criteria.

Now that most teams are hip to the ways of WAR, they are going to play rookies with better WAR potential, rookie being susceptible to this pressure because they are team-controlled, as opposed to the pool of all players, where WAR will even out every year because it has to, by the metric’s design.

That’s also why we see rising Ks rates for pitchers, now that we care more about K rates for pitchers (and less so for hitters, the pressure in the opposite direction) or why we’ll start to see better pitch framing abilities in catchers (since there’s no opposing selection pressure in the other direction), and so on.

It’s not the whole story, but look at the numbers from 2002 (moneyball)-2015.

Ben
Guest
Ben
6 months 13 days ago

I’d be curious to see what’s happening on the other end of the spectrum. WAR for players 35 and up, for example.

pft
Guest
pft
6 months 12 days ago

Lowest WAR since 1979 and fewest PA since 1993

vince
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vince
6 months 13 days ago

Inexperienced (read less skilled) players are taking up a larger share of the league. They are feeding off of the subsequent lower talent level. The net result is a watered-down overall product. A fine recipe for mediocrity!

pft
Guest
pft
6 months 12 days ago

At times in recent years I do feel as if the talent pool of players on the field has declined. Part of this may be the low pay in the minors driving many athletes towards other sports. Older players make more, younger players make less. Its not hard to understand why owners would tend toward this direction, especially if they don’t place as high a premium on winning since with revenue sharing, RSN deals, national TV deals, MLBAM, rising franchise valuations, etc, the revenue from attendance is a smaller part of overall revenues. There really is no compelling need to win. Teams can increase profits simply by cutting payrolls

Eric
Guest
Eric
6 months 12 days ago

I have been arguing this for years. In fact, I have stated that the 1980s was the LAST GREAT DECADE in MLB.

More stolen bases, slightly less success rate.
Better pitching
Better hitting
Better rookies, who is going to argue with Wade Boggs, Tony Gwynn, Cal Ripken Rickey Henderson, Willie McGee, Don Mattingly, Roger Clemens, Barry Bonds, Mark McGwire, Jose Canseco, Tim Raines, etc

10-12 of the 300 game winners either ended their careers or were rookies in the 1980s

12-14 of the 3,000 hits players either ended their careers or were rookies in the 1980s

Other than Kenny Lofton, the last of the prolific base stealers flourished in the 80s.

Game was better more overall contact, more overall hits, more overall consistency.

The only aspect of the 1980s that was worse? the defense. I concede the modern game kicks ass in that department.

You're Wrong
Guest
You're Wrong
6 months 12 days ago

Steroids.

kev
Guest
kev
6 months 12 days ago

Article must exclude Braves rookies :(

Paul G.
Guest
Paul G.
6 months 12 days ago

Define “rookie.” Are these players making their major league debut, even if it was only a cup of coffee in September, or are there some sort of threshold like the Rookie of the Year Award?

Who_Is_Zorbist
Guest
Who_Is_Zorbist
6 months 12 days ago

Sou you’re saying the Phillies will be good this year, right?

replevel
Guest
6 months 11 days ago

Wild speculation here, but I wonder if this has something to do with pitcher velocity. As more and more big-league pitchers started throwing 98 and 99 in recent years, hitters who came up against minor leaguers maxing out at 91 and 92 had to adjust to keep up. Assuming there are more guys throwing 97 and 98 in the minors (this is just an assumption- I have no data to back it up, but it seems likely) and the gap between MLB and MiLB pitching closes, these rookies are more ready for major league pitching than previous classes were. Am I crazy?

Hurtlocker
Guest
Hurtlocker
6 months 11 days ago

This is an exciting time for baseball, you wonder if rookie success translates into more kids wanting to play baseball??

David
Guest
6 months 9 days ago

This article begs the obvious question – What the fk does WAR mean? How can you use an acronym over and over again and not tell us what it means? I’ve been a sports fan all my life, and while I haven’t followed baseball closely for a few years, I still expect to understand a basic article telling why a rookie class is the best in 100 years. I’ve gone over it in my head a dozen times, but I can’t figure it out. Wins Against ReallyGoodTeams? WinsAbsolutelyRidiculous? What About ReliefPitchers? At least explain to us what you’re talking about.

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