The NBA (and NHL) Finals Could Be a Championship Sweep. We Don’t See Those Much Anymore.
Across the series-based major men's pro sports, we're running way behind how many championship-round sweeps "should" happen.
(Note: This story was originally published before the Florida Panthers took a 3-0 lead in the Stanley Cup Final, giving them a chance to join the list of championship sweeps as well.)
When the Boston Celtics and Dallas Mavericks face off in Game 4 of the NBA Finals on Friday night, the Mavs will be trying to take the first steps toward making history — attempting to become the first NBA team ever to come back from down 3-0 in any series, ever.
But the Celtics will also be trying to do something that’s rarer than it seems like it should be: Simply sweeping a championship series.
The NBA has only seen one Finals sweep in the past 17 years — when the Golden State Warriors ran roughshod over the Cleveland Cavaliers in 2018 — and only three in the past 29 years. And basketball isn’t alone — MLB has only seen one World Series sweep since 2007, and the NHL hasn’t had a Stanley Cup sweep since the Red Wings beat the Capitals all the way back in 1998, 26 years ago.
If you’re counting, that means the three series-based major men’s pro sports finals have had just two combined sweeps in the past 17 years.
There was a time when championship-round sweeps were a lot more common. During the 1990s, there were nine total sweeps across those three leagues: Five in the NHL, three in MLB and one in the NBA. But that number has dwindled with time. In the 2000s, only five championships went 4-0 (three in MLB and two in the NBA); in the 2010s, just two did (one in MLB and one in the NBA); and none have done it in the 2020s yet.
Of course, maybe we shouldn’t expect that many sweeps in the Finals or the World Series. After all, the title round theoretically would feature two of the best — and more importantly, most evenly matched — teams in the league each year. Perhaps it’s just really difficult to beat another great team four times in a row, including twice on the road. So how many sweeps should we expect under normal circumstances anyway?
We can try to answer this by looking at the pre-series Elo ratings for both championship competitors in each league, each season. Since the Elo ratings can be converted to win probabilities (at either team’s home venue), we can also calculate the odds of a sweep by either team. For instance, based on the pre-series ratings for the Celtics and Mavericks, we’d have expected there to be a 12.6 percent chance of a sweep going in: 10.2 percent for Boston and 2.5 percent for Dallas.1
According to that method, here’s a look at cumulative actual versus “expected” sweeps by year since 1990:
From 1990 until about 2007 or so, we were getting roughly as many sweeps as we would expect based on the Elo ratings. (Sometimes we’d be running at a slight surplus, sometimes at a slight deficit, but it tended to even out to net-zero.) But then something happened. Aside from the San Francisco Giants’ rather stunning sweep of the Detroit Tigers in the 2012 World Series (Detroit was actually a fairly solid favorite beforehand) and the aforementioned 2018 Warriors’ sweep of the Cavs (an, um, less surprising result),2 even the most lopsided title bouts have failed to yield sweeps as often as we’d expect.
Which leads us to the obvious question: Why?
The conspiratorially-minded among us might immediately suspect that this is somehow related to the fact that TV networks, advertisers and various other entities invested in selling the Finals as an entertainment product didn’t spend all of that money to have a short, less-than-compelling series conclude the season. As a hardened cynic myself, I can understand that impulse — although it’s difficult to understand the mechanism by which it would happen, aside from suspect officiating. (And who would have watched the fourth quarter of Celtics-Mavs Game 3 and thought the refs were trying to avert a sweep?)
Perhaps a less shady explanation is just that underdog teams are learning how to exploit the favorite’s weaknesses better than before, if just for a game or two — just enough to prevent a sweep. (The so-called “Gentleman’s Sweep,” a 4-1 series outcome, has increased steadily in frequency since the 1990s, lending credence to this theory.) Or it could be that recent changes in series format, particularly in how rest and travel days are spaced out, could help underdogs play more to the best of their abilities as the series goes on.
(Subscribers, please give me any of your additional theories in the comments below. I am seriously curious what everyone thinks might be causing the death of sweeps!)
Whatever the root cause, it’s clear that championship sweeps are just not a thing that happen anywhere near as much as they used to. Which would make what the Celtics are trying to do all the more impressive: In an age of invisible forces working against the sweep, Boston has a chance to break out the brooms anyway.
Filed under: Statgeekery
The odds don’t perfectly add up to the total because of rounding.
Golden State was -1075 to win before the Finals, which equates to a hilariously high 91.5 percent implied probability before taking out the vig.
I don’t disagree with that assessment of the trend toward more competition and greater parity over time. That said, the Elo-based expected sweeps measure should in theory account for changes in the distribution of team strength over time. Yet even after controlling for more competitive matchups on paper, we get fewer sweeps than we “should”.
The lack of sweeps is a symptom of a much larger seismic change in sports over time. Specifically, as talent has been allowed to move more freely within sports, the landscape has become more competitive and there are fewer dynasties and sweeps as a result.
Recall, that in the 1950s it was frequently noted - accurately - that the Yankees' AAA farm team was superior to most MLB teams at the time. A handful of teams had a virtual monopoly on talent and most races were over after the All-Star Break. Consequently, fan interest outside of those few teams was not high. Just consider how much of baseball's history in its first 50 years is confined to those few teams versus the last 50.
As an A's fan who watched as they won three straight Championships in the early 70s with a Coliseum often not at capacity during the Series, I watched with great interest when the Seitz decision was handed down in 1975 and the reserve clause effectively eliminated. Laser focused because the A's saw an immediate drain of talent and the media uniformly told me that free agency would "ruin baseball."
They were wrong...it was the opposite.
The game quickly became more competitive and interesting to a wider swath of fans. As the supply of talent was able to move more freely to satisfy demand, monopolies on talent were reduced and greater competition was fostered. The results were immediate. Races were closer, often coming down to the final weeks. Championship banners were no longer a fait accompli as Bob Cousy so candidly noted recently.
Importantly, with family-owned baseball teams (many of which viewed their team as a mere hobby) now less able to make money through artificially low labor costs, teams began to be sold to new aggressive ownership groups who were successful in other lines of business. These new owners were familiar with the rigors of the marketplace and what it took to be successful. They brought with them money and new ideas that expanded the competitive landscape. It is not an overstatement to say that the entire Moneyball fervor was the direct result of the Seitz decision 25 years earlier.
Additional changes have been felt in other ways as well through efforts such as elimination of discriminatory color lines, franchise expansion, challenger leagues (e.g. the AFL and ABA), salary caps, Draft incentives and luxury taxes. In each case, these developments allow for greater movement of labor and increased competition among teams.
Consider how much time today is taken up talking about roster construction versus just a decade ago. Consider also that the Washington Capitals just bought CapFriendly - a free website - to help them manage the cap. This is all the result of increased labor movement and pay - and is a great thing for fans - even if the media is so often oblivious to their impacts.
Yes, the Chiefs won the Super Bowl - but could have easily lost to San Francisco. Some of the Patriots' Championships came down to one or two key plays. Injuries aside, the difference between professional sports teams today is razor thin. Boston is not that much better than Dallas, and neither are the Panthers compared to Edmonton - even if they both sweep. Don't be fooled - just ask the Nuggets who were anointed as a dynasty just a year ago.
The game today is more competitive and entertaining for everyone when there exists greater labor freedoms and fewer dynasties and sweeps.