Nylon Calculus: What does it mean to steal homecourt advantage?

As the seconds ticked down on Game 2 in Toronto Sunday, some hundred sportswriters set to work on some hundred ledes. Each would have their own interpretation of what had transpired in the series’ second act, but they would mainly be variations on a tune. Strip away the details, and playoff recaps are expected to have certain elements — specific facts, or at least wisdoms steeped so deeply in convention that it’s all the same to readers at this point.

Boil it down, and the routine essentially becomes an equation. A mathematical proof to dictate the series narrative.

We know Golden State to have 109 points.
We know Toronto to have 104 points.
We know the game to have concluded.

Therefore: Golden State has won.
Therefore: The NBA Finals are tied 1-1 heading to California.
Therefore: The Warriors have stolen home court advantage.

What does that actually mean, though — “stealing” home court?

On its face, it seems pretty straightforward. Heading into Game 3, Team B has the advantage of having more remaining games at home than on the road, so if they manage to win at least one game that Team A “should have won,” they usurp Team A’s status as the team in control of the series outcome. Is that actually true, though?

Or rather, to what extent is it true?

It’s self-evident that a team that wins one game instead of zero games is going to be in a more fortuitous position in a game of first-to-four. But does that mean the pendulum has swung all the way in the opposite direction to where they are now the series favorite? Have they merely canceled out the hosting team’s original advantage? Is there even more mountain left to climb before they’re on even footing? Calling it “stealing” an advantage would indicate that it’s the first of the three, but how often is that actually the case? After all, Team A had home court advantage to begin with for a reason.

As it turns out, the answer is… well, it depends.

The simplest way to get at the heart of the issue is to just dig up every playoff series in NBA history, take a gander at what happened when the road team drew a split in the opening salvo and draw conclusions from there. However, it’s important to try to isolate out as many confounding variables as possible, and in the entirety of NBA history, there are no shortage of options. The introduction of the shot clock, the ABA merger, the 3-pointer, first round byes, best-of-three, best-of-five, 2-3-2 format, the occasional weird 1-2-2-1-1 format, LeBron James’s existence… the list goes on and on.

The setup that probably yields the largest data set while maintaining generally consistent conditions — and the one that we’ll be using — is every best-of-seven series that followed a 2-2-1-1-1 format since the introduction of the 3-pointer in 1979-80. Furthermore, since it’s unlikely a 1v8 matchup in the first round is going to play out the same way as a showdown between the top two seeds in the conference finals, let’s split these up by seed margin as a rudimentary stand-in for relative team strength. (Initially, I drilled down by round as well, but any flicker of signal coming from one round vs. the next appears to just be a function of the convergence of typically high seed numbers as you get deeper into the playoffs.)

The three groups we’ll examine are series where the team with homecourt advantage was five or more seeds above their opponent (5+ Gap), series where the team with home-court advantage was between two and four seeds above their opponent (2-4 Gap) and series where the team with home-court advantage was zero or one seeds above their opponent (0-1 Gap). Due to a quirk in playoff seeding, there have been several instances where the team with homecourt advantage was actually the worse seed against a division winner (sometimes by as wide a margin as the No. 6 seed hosting the No. 3 seed). These cases will be treated as part of the 0-1 Gap, with the team holding homecourt advantage treated as the, well, team with homecourt advantage.

The last thing to note is that we won’t be looking at the final outcome of each series. We will instead note where the series score stood when games returned to the first city after Game 4. What’s important here isn’t necessarily who wins or loses the series as a whole, but whether teams that “steal” home court from their opponents in Games 1 and 2 actually sustain that advantage over the course of the series. If a team loses Game 2 at home but returns for Game 5 with the series knotted at 2-2, that doesn’t seem meaningfully different than if the vaunted advantage had simply held serve for both sides.

The Robin Hood effect

Regardless of what Michael Douglas says, greed isn’t always good. Especially when you’re a spectating fan and one team just gobbles up all the wins from what you were hoping would be a competitive series. It should come as no surprise that the most frequent offenders belong to the group that, save for some sickos like the 1999 Knicks, is exclusively comprised of No. 1 vs. No. 8 and No. 2 vs No. 7 matchups in the first round.

Over two-thirds of these series see the heavy favorite take a commanding 2-0 lead, and that tends to be curtains when they collectively average more than one win from the two road games. In cases such as these, winning a game or two on the road as the underdog isn’t so much wresting control of the series as it is just merely giving your side a chance.

Among the 397 series examined, 185 of them saw one team take a 3-1 lead through the first four games. And though as noted above, the series outcome isn’t necessarily what we’re focusing on here, it’s worth noting that a whopping total of eight teams managed to come all the way back from down 3-1 to win a series in that span. Of those eight, only two didn’t have homecourt advantage for Game 7. Simply put, winning one of the first two on the road for 5+ Gap teams is a matter of series life and death.

It’s not stealing if you don’t get caught

The second group tends to be a bit more of a mixed bag, which makes sense as it’s the largest group as well, drawing from a first-round matchup, a minimum of one second-round matchup and any number from thereon out.

It’s here, though, that we start to see some of the pattern emerge. Regardless of whether the team with homecourt advantage hits the road up 2-0 or tied 1-1, they historically have virtually identical odds for coming away with a win on the road — and near even odds at that.

Another way of interpreting this is that while a team that takes a 2-0 lead is not necessarily in the clear, the odds being slightly tilted towards getting swept on the road, the road team stealing one of the first two isn’t so much a sign of an upset as it is a strong indicator of a series that could legitimately go either way.

Interestingly enough, despite the averages, the percentage of 2-4 Gap series that end up 2-2 isn’t substantially higher than that of the 5+ Gap group. So, while the risk of going down 3-1 is significantly greater (32.5 percent) for teams facing a 1-1 tie, there’s also a fairly strong chance (20 percent) the series favorite will return home leading 3-1.

This is the Bad Place

You can see where we’re going, so I’ll just lay it on you.

At a glance, this probably doesn’t look as bad as you expected, but give it a moment. Let’s go through it piece by piece.

The first thing that likely jumps out is the Expected Wins Through 4 resting precariously close to an even 2. Going into these series, the default — not just for teams that drop a game at home but the overall expectation — is a 2-2 series draw. Unsurprisingly, teams heading into Games 3 and 4 on the road with the series tied only return home up 3-1 one out of every eight times. Contrast that with the 39 percent of the time they’re down 3-1 heading into the turn. Much like underdogs in the 5+ Gap group, teams that drop a home game in a series like this are effectively fighting for their playoff lives.

Making matters worse, the average favorite in a 0-1 Gap series wins about 65 percent of their games at home… which means the probability of them winning both Games 5 and 7 at home is only 0.42. For a team that stumbles out of the gate early, not only is it harder to make that back up on the road but it’s also significantly harder to stay afloat on their own court moving forward.

It’s this group that I would consider genuinely stealing home court. Winning a game on the road when you’re an underdog tips the scales towards uncertainty, but when it happens in a series where the margin for error is so fine, it legitimately does go so far as to tip the odds into the underdog’s favor for the series at large.

One last thing

A wise sage once said: “Don’t turn your back on the Wolfpac.” Whether or not anyone knew it at the time, that was actually referring to LeBron James.

Over the course of his career so far, James’s teams have been the on-paper underdog in 14 series. In those 14 series, when his teams have headed home for Games 3 and 4, they’ve come away with an average of 1.43 wins. For every team that doesn’t have LeBron James, that number is 1.07.

So, if there’s one thing to take away from this, it’s that when a team “steals home court,” more often than not, it can be taken right back… unless you’re playing LeBron. Then that thing’s gone.