Is Covering the Spread Sustainable? Lessons from the NBA

Steph Curry looking at the scoreboard
By Noah Salzman (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

Is posting a great (or miserable) record against-the-spread one season a solid indicator that a basketball team will do the same the next year? Or is it the other way around: do teams tend to revert to the mean? That’s the question of the day and, as always, the internet has the answer.

Let’s start by looking at the top five ATS teams from the last five seasons and juxtaposing their results with their performance the next year. (Data taken from TeamRankings.com.)

 TEAM
2011-2012 ATS RECORD
2012-13 ATS RECORD
Spurs
49-27-4 (64.5%)
53-48-2 (52.5%)
Bulls
41-30-1 (57.8%)
41-53-0 (43.6%)
 Raptors 37-28-1 (56.9%) 41-40-1 (50.6%)
Hawks
39-31-2 (55.7%)
39-47-2 (45.4%)
Warriors
36-29-1 (55.4%)
51-42-1 (54.8%)

 

TEAM
2012-2013 ATS RECORD
2013-14 ATS RECORD
Grizzlies
57-38-2 (60.0%)
40-46-3 (46.5%)
Mavericks
48-34-0 (58.5%)
50-39-0 (56.2%)
 Thunder  52-39-2 (57.1%)  52-48-1 (52.0%)
Wizards
45-35-2 (56.2%)
50-42-1 (54.4%)
Nuggets
49-39-0 (55.7%)
39-43-0 (47.6%)

 

TEAM
2013-2014 ATS RECORD
2014-15 ATS RECORD
Suns
52-29-1 (64.2%)
41-39-2 (51.2%)
Hornets
48-35-3 (57.8%)
39-41-2 (48.8%)
 Raptors  48-37-4 (56.5%)  37-48-1 (43.5%)
Mavericks
50-39-0 (56.2%)
37-48-2 (43.5%)
Spurs
58-47-0 (55.2%)
45-42-2 (51.7%)

 

TEAM
2014-2015 ATS RECORD
2015-16 ATS RECORD
Celtics
50-35-1 (58.8%)
45-42-1 (51.7%)
Rockets
58-41-0 (58.6%)
38-49-0 (43.7%)
 Hawks 56-41-1 (57.7%)  45-45-2 (50.0%)
Pelicans
49-37-0 (57.0%)
36-46-0 (43.9%)
Warriors
58-44-1 (56.9%)
59-45-2 (56.7%)

 

TEAM
2015-2016 ATS RECORD
2016-17 ATS RECORD
Warriors
59-45-2 (56.7%)
41-40-2 (50.6%)
Magic
45-36-1 (55.6%)
32-48-2 (40.0%)
 Mavericks  47-39-1 (54.6%)  43-38-1 (53.1%)
Heat
51-44-1 (53.7%)
48-33-1 (59.3%)
Knicks
44-38-0 (53.7%)
42-40-0 (51.2%)

 

The first thing that jumps out is that only one team (the 2016-17 Heat) was able to better its ATS record after finishing top five the previous season. Only three (2016-17 Heat, 2015-16 Warriors, 2013-14 Mavs) were able to stay among the top five.

On average, top-five finishers saw their cover-rates drop by 7.5-percent, and 11 of the 25 teams weren’t even able to stay above .500.

But what really stands out here is the way the best of the best plummet. The ten biggest declines all came from teams that started at 55.6-percent or higher, and every team that finished 59-percent or better fell at least 10-percent the next season.

What does it mean for next year?

We’re not going to delve too deeply into the “why” of these regressions. Suffice to say, there’s no single answer. Sometimes rosters change drastically in the offseason. Sometimes sportsbooks are simply adjusting lines. A multitude of factors go into it. But the stats clearly show that excellent ATS records are not sustainable from one year to the next, especially for the true outliers.

That’s important to keep in mind. Bettors tend to fall in love with the teams that win them money. The start of a new season means you have to hit the reset button on your romance.

Who should you be shying away from in 2017-18? To start, here’s this season’s top five:

TEAM
2016-2017 ATS RECORD
76ers
49-33-0 (59.8%)
Heat
48-33-1 (59.3%)
 Nuggets 46-36-0 (56.1%)
Thunder
46-37-1 (55.4%)
Mavericks
43-38-1 (53.1%)

 

Based on the trends I laid out, the two teams to approach with extreme caution are Philadelphia and Miami. As mentioned, in the last five seasons, every team that has covered at a rate of 59-percent or better has dropped by double-digits the next season. If that holds true for the Sixers and Heat, they will be sub-.500 ATS teams in 2017-18.

If the other three teams in the top five regress by the average 7.5-percent, they will all have sub.-500 ATS records as well.