The Dodgers won a game.
For the lion’s share of the 2017 Major League baseball season, the above sentence was an apt description of the Dodgers result on an almost nightly basis. Indeed, as of their off-day on August 28th, the baseball world was talking about the Dodgers — owners of a 91-38 record and a staggering +219 run differential — as worthy challengers to the 2001 Seattle Mariners for the crown of best regular season team in history. Through that date, the team had already managed to string together multiple 10+ game winning streaks, win 20 games in a month twice, and build an insurmountable National League West division lead. Sports Illustrated even ran the following cover on August 22:
Since the off-day on August 28th, however, the once-invincible Dodgers have played historically bad baseball, losing 14 of 15 games through September 11 — including an astonishing 11 games in a row. They were outscored by 53 runs over that stretch, a truly unbelievable fall from grace for a club that was crushing teams for most of the season. Suffice it to say that it’s a good thing SI included that question mark on their cover.
Interested parties across the country have been pushing the panic button. Take, for example, Bill Plaschke of the LA Times, who pronounced on September 7th that the Dodgers’ season was “spiraling out of control.” Similarly, Plaschke’s LA Times colleague Andy McCullough answered fan questions in an article titled, “Dodgers mailbag: It is time to panic.” McCullough wrote:
It is an abysmal skid, a horrific skid, an embarrassing skid, a confounding skid. I am running out of adjectives to describe it. This is my eighth season covering Major League Baseball. I’ve never seen anything like this — and I used to cover the Mets.
So, what to make of all this? Is it really time for Dodger fans to panic about a team that seemed destined for greatness only three weeks ago? Probably not, and let me tell you why.
Observed outcomes and randomness
First, we need a quick refresher. Every observed baseball statistic (e.g., wins, batting average, ERA, fastball velocity, etc.) has some degree of randomness involved. A hitter’s batting average, for example, is dependent not only on his underlying ability to hit but also elements of randomness outside of his control such as a weird hop of the baseball or a missed call by the umpire. Generally, then, observed statistics take the following form:
Observed Outcome = True Talent + Random Noise
Some observed statistics — such as a hitter’s batting average on balls in play or a team’s ability to cluster hits together to score runs — are almost completely random, while others — such as a pitcher’s fastball velocity or a hitter’s foot speed — are almost all talent and have very little random variation. Regardless of the statistic, over the course of many trials, we expect a player (or team’s) true talent to shine through and for random variation to even out. However, over a small, arbitrary sample size (e.g., 15 Dodger games in early September), the randomness can cause wild results. I think most baseball fans understand this.
Here’s the real issue. Those perplexing, random results often masquerade themselves to us as a pattern, causing both casual fans and more-informed pundits to create a narrative that a structural change in the player or the team is causing the results. Stanford PhD Ed Fang elaborates:
Humans have an uncomfortable relationship with randomness because we are wired to see patterns, as Daniel Bor explains in his book The Ravenous Brain. It starts with counting by 2 and 5 in the earliest years of grade school and culminates in the technology that puts a computer in our pocket. Humans have this remarkable ability to find patterns even though we can only hold 4 items in our working memory, the same number as a monkey. […] Humans not only find patterns but then tell stories to explain them.
According to Fang, humans are wired to build narratives around patterns that we perceive as being real but that are actually due to randomness. In my opinion, there is something about sports — perhaps the human aspect — that exacerbates our propensity for building narratives around fake patterns of outcomes.
To illustrate what I mean, I flipped a coin 30 times. In those 30 flips, I came up with 9 heads and 21 tails. The coin was very streaky also, landing tails 11 times out of 12 tosses at one point! Now, I don’t think these results would cause most people to conclude that the coin is weighted or not fair; I feel like most people are very aware of the inherent randomness involved in a small sample of coin flips. What if, however, we were analyzing wins and losses for a baseball team rather than heads and tails flips of a coin. In that scenario, you can bet that 9 wins out of 30 games — including 11 losses out of 12 — would cause most fans to search for a story to explain the losing. The context of sports causes us to forget that randomness plays a role.
So, then, both talent and randomness effect observed outcomes — in this case, the Dodger’s streak of losses. Has there been a structural change in the Dodgers’ talent (e.g., injuries or fatigue), or have they been victim of some sort of horrible (random) streak of regression? Let’s take a look at their season to-date in an effort to find out.
Before the off-day on August 28th
The Dodgers were a juggernaut prior to August 28th — thanks in large part to both the hitters and pitchers playing well above their preseason projections. Preseason projections are never exactly right, but they give a window into industry expectations of a player’s true talent levels. We would expect players who are playing well above projections to fall back to earth as the season continues.
Below is a graph showing actual minus preseason predicted weighted on-base average (wOBA) for the Dodger hitters through August 28th. (Projections are per Steamer, and data per Savant.) As I’ve mentioned before, wOBA is an effective measure of the overall contribution of a hitter. It is an improvement over on-base percentage because it rewards hitters for the exact run values of distinct offensive events (singles, doubles, walks, etc.) by using linear weights.
Red bars indicate those players that were under performing preseason projections as of August 28th, and blue bars indicate those players that were over performing. As the graph shows, most of the Dodger hitters were — for whatever reason — well outperforming their projections during the first five months of the season; it is natural for hitters like Chris Taylor and Austin Barnes to regress as the season progresses. This is random variation at work, and we should expect it. The same is true for certain Dodger pitchers, as shown in the graph of actual minus preseason predicted WAR below.
Again, red bars indicate under performance relative to projections, and blue indicate over performance. As the graph shows, certain key arms such as first-half stud Alex Wood and reliever Brandon Morrow were punching way above their projections for the first five months of the season. Just like with hitters, we should expect these guys to come back to Earth.
It seems the Dodgers benefited from a perfect storm of many hitters and pitchers outperforming projections at the same time. This is what allowed the Dodgers to rattle off a stretch of winning like they did from May through July. Regression was inevitable. Sure, the true talent projections could be wrong; perhaps Chris Taylor is a much better hitter than the industry gave him credit for. However, I’d also argue that both the hitters and pitchers were getting randomly lucky and that this luck was always bound to reverse.
Let’s look at hitters first. Below is a graph showing actual wOBA minus expected wOBA for Dodger hitters. Expected wOBA is a Statcast statistic that measures what the wOBA for a given hitter should have been based on the exit velocity and launch angle of his batted baseballs. Expected wOBA removes the actual outcome (e.g., single, double, triple) from the equation and rewards hitters for what they can control (i.e., the quality of contact). A hitter with a large difference between actual wOBA and expected wOBA has gotten lucky.
Red bars in this context mean unlucky hitters, and blue bars indicate lucky hitters. As the graph shows, through the first five months of the season, almost every Dodger regular posted an actual wOBA higher than would be expected given the quality of the contact. Some, such as Chris Taylor and Yasmani Grandal, posted significant deltas (above 0.04). According to Fangraphs, an increase of 0.04 in wOBA can mean the difference between an average season and a great season. Remember, these differences are due to random variation driven by the positioning of the defense, umpires, weather, etc. It was inevitable that the luck would turn around.
The same goes for the two pitchers we mentioned above who were uncharacteristically successful in the first five 4-5 months.
The luck is less pronounced on the pitchers’ side, yet it’s clear that the results posted by Alex Wood and Brandon Morrow were lucky based on the quality of contact allowed.
After the off-day on August 28th
We’ve seen that both Dodger hitters and pitchers were over performing their projections, thanks in part to random luck. Since that date, basically every Dodger player has regressed. The team results speak for themselves, and the media has scrambled to explain the losing.
But that doesn’t mean that the team is any different than the team we were watching three weeks ago! Indeed, there is evidence that — in this tiny sample size — the hitter and pitcher luck has turned against the team. Let’s look at the same graphs as above, except this time we’ll filter for games after August 28th.
Red still means unlucky, and blue means lucky. As shown in the graph, the luck has reversed itself in this tiny sample size, as most Dodger hitters have hit the ball better than their results would indicate. The same goes for pitchers:
Based on the contact allowed, almost every Dodger pitcher has pitched better during the losing skid than their results would indicate.
There’s no way around it: the Dodgers have been playing bad baseball. But as these two graphs show, they have also been getting unlucky!
Where we stand
Let’s return to our primary question: what explains the observed losing? Has there been a structural change in the Dodgers’ talent, or has randomness showed up at an inopportune time?
I’d argue a bit of both. There’s little doubt the Dodgers are fatigued, as every team is to some degree at this point of the season. Clayton Kershaw and Corey Seager have also missed time due to injury; without those two healthy, the Dodgers are not nearly as good as they could be. Their psyche is probably a little shaken as well from the last two-weeks of losing.
Yet it’s important to remember that randomness is involved, and I think the panic narrative built by the fans and media alike is foolish. The Dodgers, perhaps more than any other team, were due for some regression. Randomness does not explain the entire streak, but it is certainly a contributing factor.
So, what should we expect going forward? As the late NFL coach Denny Green famously proclaimed, “They are who we thought they were!” As long as they are healthy, we should expect the Dodgers to get back to their winning ways. They have a deep lineup and bench, Kershaw and Darvish at the top of a stacked rotation, and enough bullpen arms to match-up with the best of teams. Their bullpen improved at the trade deadline, and they have strong leadership in the clubhouse. In short, expect the Dodgers to be the Dodgers. Mike Petriello, who is a friend of the MIT Sloan Sports Analytics Conference and an overall great guy, said it best when asked what the Dodgers need to do to turn their September around:
The unluckiness will subside, and the Dodgers will get back to winning games. Of course, this doesn’t mean that they will win the World Series. If you take away anything from this article, it should be that baseball in small sample sizes — like the postseason — is subject to a ton of random variation. Yet the Dodgers are in a fantastic position, and I can’t wait to see what happens.
Update: Since I began writing this article last week, the Dodgers have won 3 of 4 games, and the chatter about collapse has predictably subsided. Pretty soon, the media will be talking about how “hot” the Dodgers are leading into the postseason! Beware of the narrative.