Is the NWSL Playoff Format Stacked Against Top Seeds?

There’s been a lot of talk in sports lately about playoff formats, and whether top seeds are inadvertently being disadvantaged with byes, extra time off and so forth. The NWSL, which will play its 2023 championship on Saturday between a No. 4 seed (OL Reign) and a No. 6 seed (Gotham FC), has as much room for discussion as any league. 

Including this year, the three seasons of the league’s current playoff format — which gives the top two seeds byes into the second round of the three-round knockout bracket — have seen just one top-two seed advance to the final in six tries. The outlier? In 2022, the Portland Thorns advanced to the NWSL Championship – and won – as a No. 2 seed. 

It might be tempting to write off the results of three seasons as just small-sample noise, particularly when things go like they did in this season’s semifinals: The lower-seeded team knocked off the favorite in each game by a slim 1-0 margin, including Katie Stengel’s dramatic 107th-minute game-winner that gave Gotham FC the late victory over Portland. But favorites going 1-for-6 is such a jarring record that we thought it deserves some extra investigation.

And as things turn out, it is such a statistical anomaly that there may actually be something to the top-seed-disadvantage narrative.

To test out just how improbable it would be for top seeds to lose as often as they have, we used our NWSL power ratings to simulate the playoff brackets from the 2021, 2022 and 2023 seasons. The idea is to establish the odds that simple chance alone might produce such a three-year run of futility for favorites, after accounting for the strengths of the teams involved (as well as factors such as home-field advantage).

In 1,000 simulations, there were cases of equal or even greater failure for top seeds. (Simulations No. 285 and 787 each saw a clean sweep against favorites — 0-for-6.) But that was rare. Just 19 times in 1,000 chances did the simulations send one or fewer of the top two seeds to the final over a three-season span. In other words, there’s less than a 2% probability that top seeds would struggle as much as they have out of pure chance alone — meaning that, most likely, something deeper is happening.

In theory, securing a top seed should mean a big advantage headed into the playoffs. Byes are supposed to be beneficial. If you earn one, it means having one fewer opponent to potentially end your season — which seems worth fighting hard for if you are within striking distance of the top two in the standings.

We can see this in how the simulations played out: Based on the ratings of the teams involved, No. 1 seeds should have had a 65% chance to make the championship final per season in our simulations — and No. 2 seeds a 66% chance — with no other seed number sitting any higher than a 21% chance to make the final. 

But clearly, those odds are being defied somewhere along the way. The big question is why?

As usual, the leading potential culprit is the age-old debate of rust versus rest. And in the NWSL, that question is complicated by the confluence of the league playoffs with an international FIFA window. 

In the case of this year’s top teams, No. 1 San Diego and No. 2 Portland went 21 days — from Oct. 15 and Nov. 5 — between games, the result of the bye and a one-week international-window break that fell right in the middle of the postseason. While their opponents had a 14-day break between action heading into the semifinals, the extra week might have tipped over from a useful break to a harmful layoff.

That’s been true each of the past two seasons, with the gap between regular season’s end and playoff debut for first-round bye recipients expanding from 14 days in 2021 to 21 days in both 2022 and 2023:

Not everyone considers the bye a disadvantage, of course. After her OL Reign were given a bye, and then knocked out of the semifinals for a second straight year in 2022, coach Laura Harvey said she didn’t think the extra time off played a role in the loss.

“No, I've said this before, I don't think that the bye was a disadvantage to us at all,” she said. “I don't think that contributed to the game, if I'm honest, because we would have gone into the game last week really fatigued and we weren't tonight, so I'm not going to use that as an excuse. No chance.”

Along similar lines, the great Megan Rapinoe also rejected the rust narrative following that game.

"I don't really think [the bye was a factor]. Personally at least, I can't imagine having to play last week after having to go abroad and play two games and play a lot of minutes and a lot of us here, (defender Alana Cook) Lani, (midfielder) Rose (Lavelle), (defender Sofia Huerta) Sof and I all played a lot of minutes abroad, so I don't think so,” Rapinoe said. “I felt like we were in a good rhythm, had a good week of training, felt like it was actually nice to get a little bit of a break and get everybody's body right. I mean, you never really know, but I don't think that that's really what happened tonight."

A year later, Rapinoe and the OL Reign are finally playing in an NWSL championship again – this time as a No. 4 seed that didn’t have the theoretical benefit of a first-round bye.

The placement of the international window during the playoffs makes this type of analysis especially tricky. It’s not just a debate over rest vs. rust, but also one involving fatigue of a different kind. San Diego had six players logging international duty during its extra “off” week, and Portland had five.

How much did that matter? It’s hard to say, as the semifinal winners also had a number of players join their respective national teams during the break. (OL Reign actually saw seven players leave for international duty.) 

Still, speaking from a statistical standpoint, it’s unlikely that quite this many top seeds would go down early through the sheer power of ordinary soccer chaos. Whether the rest/rust factor, the international absences or something else, the disadvantage for top seeds seems to be a real phenomenon, and the NWSL might want to figure out what to do about it before next year’s playoffs.