Dr. Diandra: How much does Talladega shake up the playoffs?

Talladega Superspeedway is known for shaking up the playoffs. But how well deserved is that reputation?

Playoff drivers usually view the first race in the second round of the playoffs as the best chance to earn points, earn stage points and maybe even a win given that Talladega is the second race. Now that Texas is in the rear-view mirror, let’s turn our data analysis tools to Talladega.

The shake-up index

Determining how much one race shuffles the playoffs standings requires a simple metric that is applicable to all the years NASCAR has had stages and playoffs. In a rare point of consistency, Talladega has remained the 31st race of the season since 2017, when stage racing started.

After trying a couple different approaches, I finally settled on playoff rankings. These rankings are a zero-sum game. For each driver who moves up a position, another driver must move down.

The first graph is playoff ranking as a function of race for the second playoff segment of 2021. It’s a bit of a mess, but stay with me.

Playoff rank runs along the left side of the graph. The highest ranked driver is at the top and the 12^th ranked at the bottom.

The leftmost set of dots shows the rankings coming out of Bristol, after eliminating the lowest four drivers and re-seeding the rest. The second column of dots show the rankings after Las Vegas, which was the first race in the second round in 2021.

Each driver is represented in a different color, with lines connecting his rankings. For example, the dark purple lines show Denny Hamlin rising from third to first over these three races. The light blue lines at the bottom show Alex Bowman plummeting from seventh to 12^th.

The messier the lines between two races, the more the playoffs were shaken up. Because it’s hard to quantify “messiness,” I counted each time one driver’s line crossed another driver’s line.

Each crossing indicates two drivers changed places in the rankings. The number of intersections between Bristol and Las Vegas, for example, tells you how much Las Vegas shook up the standings.

Three intersecting lines count as three shake-ups because there are three pairs of drivers crossing.

In 2021, Las Vegas had nine intersections, Talladega 13 and the Roval only five. This seems consistent with our hypothesis that Talladega is the biggest shaker-upper in the second round.

Talladega Timeline

In addition to being only one point, the 2021 Talladega contest poses another problem. Bubba Wallace won the rain-shortened race, which went 311 miles instead of the scheduled 500 miles.

That raises the possibility that 2021 might not be the most representative year for Talladega races. I therefore repeated the analysis going back to 2017. Since we didn’t have stage racing — and thus stage points — before 2017, it doesn’t make sense to compare previous years.

The table below shows the shake-up index from 2017-2021. Note that the first and third races changed from year to year.

This five years of data show that Talladega wasn’t always the race that most shook-up this round of playoffs. From 2017-19, Dover and Charlotte held that honor. That’s surprising, especially in 2017. That’s the year 26 of 40 cars failed to finish the Talladega race and NASCAR parked Jimmie Johnson and Matt DiBenedetto.

In 2020, the three races had just about equal shake-up indices.

The Roval has been the third playoff race for only two years. It was equally chaotic with Talladega in terms of affecting the standings in 2020, but less so in 2021. Kansas beat the Roval for switching up the playoff standings twice.

 A caveat for the first race

If you’re surprised to see a larger shake-up for the first race in the second round of the playoffs, you’re not alone.

The 2021 fall Las Vegas race was remarkably uneventful. There were only two DNFs, both non-playoff cars. And one single-car accident that, again, didn’t involve a playoff car. Yet it had a shake-up index of nine.

It turns out that this is a side-effect of the re-seeding protocol.

The graph below shows the same time period as the rankings graph, but reports total points for the top-12 drivers.

Immediately after re-seeding, the drivers are separated by 57 points from first to 12^th. If you omit Kyle Larson’s 30-point lead, the bottom 11 drivers are separated by only 27 points.

Since a driver can earn a maximum of 60 points in a single race, the first race in a round has a lot more impact in changing the standings. In effect, the first race decompresses the re-seeding compression.

After Las Vegas, the 12 playoff drivers were separated by 78 points. After Talladega, the margin grew to 98 points.

The larger numbers for the first races in any round are more due to the re-seeding-induced points compression than to the nature of the track.

Applied to 2022

Drivers don’t have to win at Talladega. They just have to finish ahead of the other playoff drivers. In fact, if a given driver can’t win, the next best case for him is if none of the other playoff drivers win, either.

The largest drop in positions a driver has seen from Talladega is five — and that’s from the rain-shortened 2021 race. On the other hand, drivers have also seen as much as an eight-position gain in the standings following Talladega. That gain was after the 2017 race where more than half the field failed to finish, but at least one driver has come out of the fall Talladega race each of the last four years up at least three positions.

As far as the stats for this year’s second round playoffs so far: Last week’s Texas race had a shake-up index of 14. That’s higher than all but the first year of the stage-racing playoff era.

And the William Byron penalty (which Hendrick Motorsports is contesting) has a shake-up index of seven.