So far, it seems to me, the 2019 baseball season has been defined by three things. This might not be the case once all is said in done. Hopefully it's not. We don't know how the playoff race is going to turn out, for one. We also don't know if we will have a particularly dramatic postseason, and we don't yet know if individual statistical and awards pursuits will end up in historically rarefied air. The draft of this season's narrative remains a work in process.
Right now, in the dog days of August, there are the three dominant themes:
1. Rampant home run hitting. Whether this is a bad, good, terrible or great thing is a matter of aesthetic preference.
2. Rampant complaining about the trends in the game. Seriously, it makes one want to figure out where the internet is plugged in and just yank the cord.
3. Super young hitters putting up All-Star-level numbers. Hopefully, on this point at least, we can agree that it's an awfully exciting development. For today, we're going to focus our attention on this.
The game is skewing younger. You hear those words over and over again. Just last week, I asked Astros manager A.J. Hinch why we're seeing so many high-powered debuts such as the one he's getting from 22-year-old Yordan Alvarez. The first words out of his mouth were, "Well, the game is skewing younger." True that.
According to baseball-reference.com, the average age of MLB hitters, weighted for playing time, has been 28.1 years old in each of the past two seasons. This season's number could drop further when we get into the September call-up period. For now, that's the youngest baseball's batsmen have collectively been since 1979. This trend, and the others we'll be talking about today, doesn't really extend to the pitcher's mound, so hurlers won't get as much attention in the analysis that follows.
My task here was to examine the following question: Could we be seeing the best year for debuts in baseball history? After roughly 12 hours of squeezing a pretty large data set, I can answer that question three ways: 1. I don't know. Ask me again when the careers of these players are over. 2. Probably not, if we're talking about the group as a whole. 3. Maybe, if you zero in on star power and precocious performances.
To be sure, rookies are doing some special things in 2019. Here's one category I like: Players under age 23 who have slugged at least .590 over a minimum of 300 plate appearances. There have been three in baseball history: Ted Williams (.609 in 1939 at age 20), Albert Pujols (.610 in 2001 at age 21) and Fernando Tatis Jr. (.590 in 2019 at age 20). In one of the saddest developments of the season, Tatis' numbers are frozen because of his back injury. There won't be a run at Pujols' mark, and Tatis won't qualify in the percentage categories. This, of course, also opens up the NL Rookie of the Year race for New York's Pete Alonso. Nevertheless, Tatis has done plenty to whet our excitement for the years to come.
I picked that very narrow set of definitions because a lot of the lists I've seen of great 2019 debuts and under-23 performances have been built on slugging exploits and the related OPS category. In 1939, the overall slugging percentage in the AL was .407. In 2001, it was .425. This season so far, we're at .438 in baseball -- both leagues -- which would be a single-season record. That's even though this season's .254 composite batting average is more than 20 points lower than that of Williams' 1939 environment and 10 points lower than what Pujols dealt with. Plus, as we keep hearing, the overall MLB home run record is about to be eviscerated. This matters because though the overall levels of slugging this season have produced some eye-popping raw numbers, to judge this season as featuring the "best" of anything requires a good bit of context.
To understand whether our perception (and it's one I share) about the unusual nature of this year's group of first-timers is warranted, I deployed a database of win shares I originally downloaded from thebaseballgauge.com and have built out over time. I looked at the question of debuts in a number of ways, none of which made 2019 stand out all that much. Here are few of these approaches:
Is the sheer number of debuts unusual?
Probably, but it's hard to answer right now since we haven't hit what will be our last season of rosters that can be expanded to as many as 40 players on Sept. 1. Through Monday, we were at 210 debuts, and prorating that for the full season, we'd end up around 272. That would be a new record, breaking the total of 262 set in 2017. But of course, we're on only our 21st season of a 30-team structure, which favors the past couple of decades. It's still unusual: A final average of 9.1 debuts per team would be our highest total since 1944, when the figures were distorted by the number of players serving in the military. That means that if we keep up our current influx of newcomers, 2019 will indeed stand out historically.
What about overall debut production?
At the moment, we're on pace to get 479 win shares from players making their debuts this season. That would rank sixth on the single-season list (back to 1901). The record is 566, set in 2015. In fact, six of the nine highest single-season totals have come in the past seven campaigns. But -- again -- we're talking about more debut seasons in general and more teams. On a per-debut basis (2.28 win shares per player), this season ranks 35th since 1901. The record is 3.64, set in 1904. During the integration era (since 1947), the mark is 2.99, set in 1977. Among that season's first-timers were Eddie Murray, Lou Whitaker, Lance Parrish, Alan Trammell and Jack Morris.
What about elite debuts?
Let's define elite like this: any player who ranked in the top 100 by win shares in his debut season. This season, there are three such players: Tatis, Alonso and Pittsburgh's Bryan Reynolds. Tatis is a safe bet to remain in the top 100 even if he misses the rest of the season, as expected. Alvarez is at No. 150, and given how persistently hot he has been, it isn't impossible that he expands this list to four. However, Alvarez kind of typifies why the excitement about this year's group is a wee bit premature. Like a few of these players, he was an in-season call-up who is putting up huge numbers in what remains a small sample. We're getting to the point where that isn't a caveat we need to apply as much to Alvarez, but it remains true for Toronto's Bo Bichette and the Dodgers' Will Smith. What they've done is amazing, but let's see if they can keep it up before we start anointing this year's debut class.
Anyway, there were four elite debuts just last season: Ronald Acuna Jr., Shohei Ohtani, Gleyber Torres and Juan Soto. All of those players were under 24 years old last season, which begins to edge us nearer to today's bottom line. The total of four was the most in baseball since the aforementioned 1977 season, when there were five. There were also five in 1946, 1954, 1955 and 1961. The post-war record is seven, set in 1947, which saw a group led by Jackie Robinson, who should have debuted many years earlier.
Still, whether the final number is three or four elite debuts, it's a good total, and it's especially impressive to have seven (or eight) in a two-year span. From 1996 to 2004, there were just four elite debut seasons in total, and in six of those nine campaigns, there were zero.
That's where all of this ends up. When you judge this year's debut players as a group, they have been really good but not at a level that anyone is going to make a movie about. But within that subset of debut players, there are some amazing things being done, and it isn't a one-year story. To draw that out, let's leave aside the win shares analysis and shift over to the Play Index at baseball-reference.com. We will limit our queries to contextualized metrics (namely OPS+ and ERA+) in hopes of filtering the exaggerating effect of this year's home run melee.
Most debut players, OPS+ or ERA+ of 125 or better
2019: 8 (7 hitters, 1 pitcher)
2016: 7 (4 hitters, 3 pitchers)
2018: 7 (5 hitters, 2 pitchers)
1908: 6 (3 hitters, 3 pitchers)
1939: 6 (2 hitters, 4 pitchers)
1977: 6 (2 hitters, 4 pitchers)
2014: 6 (4 hitters, 2 pitchers)
2015: 6 (6 hitters, 0 pitchers)
1914: 5 (0 hitters, 5 pitchers)
1928: 5 (3 hitters, 2 pitchers)
1953: 5 (0 hitters, 5 pitchers)
1983: 5 (1 hitters, 4 pitchers)
Minimum: 200 plate appearances or 100 innings pitched
Source: baseball-reference.com
What we're looking at is a set of debut players who held down semi-regular roles, with relief pitchers mostly filtered out, and who performed at least 25% better than league average, adjusted for league and ballpark context. You're not reading it wrong: Barring a spate of late slumps, this indeed promises to be the most productive group of debut hitters we've ever seen. This becomes only more true if you lower the playing time minimum to accommodate Bichette and Smith. You're also tempted to add Cincinnati's Aristides Aquino to the list because, though he debuted last season, he did so with one measly plate appearance.
There's more going on here: You'll notice that five of the eight seasons on the above leaderboard have come in the past six seasons. Setting the minimum for innings at 100 filters out a lot of relief-pitching excellence, but let's face it: Who gets excited about rookie relievers? This season's lone hurler to fit these definitions is San Diego's Chris Paddack. As mentioned, this is more a hitting trend than a pitching one.
Finally, let's add a few more filters to the above list to make the category debut seasons for players age-23 or younger while leaving the pitchers out. There have been only four such seasons with at least three players who met that criteria. As you've no doubt guessed by now, they're all recent seasons:
Most debut seasons, OPS+ 125 or better by age 23
2019: Yordan Alvarez, Luis Arraez, Keston Hiura, Fernando Tatis Jr.
2018: Ronald Acuna Jr., Shohei Ohtani, Franmil Reyes, Juan Soto
2015: Kris Bryant, Carlos Correa, Miguel Sano, Kyle Schwarber
2013: Scooter Gennett, Wil Myers, Yasiel Puig
Is this the best season for debuts in baseball history? Well, I don't know. Let's see where they end up. It's certainly possible that this will turn out to be the case, especially since some of the most highly touted of this season's hitters (Vladimir Guerrero Jr, Eloy Jimenez, Nick Senzel) haven't reached the various cutoffs we've used here. They still might turn out to be the best of the group.
But when you look at this season in context -- and what we've seen over the past few years -- this much is clear: Never in baseball history have we seen this many hitters break into the majors and be this good, this young. That, my cranky friends, is the 2019 story we should be focused on.