Interesting NBA comeback probabilities
Live betting (or “in-play betting”) has truly taken the online gambling world by storm. It basically allows people to place wagers DURING games. Betting on games which are still in progress really makes games more exciting to watch. It is reported that William Hill took more than 20,000 in-play bets during the Cardiff versus Liverpool soccer game which was played on February 26th, 2012. Just imagine how much this market has probably grown since then.
Have you ever wondered, as you were watching an NBA game, what were the chances that the team currently trailing would come back to win the game? While this question intrigues many casual basketball fans, it is one that is extremely relevant to people betting on NBA live lines.
What is the probability that the road team trailing by 3 points after two quarters (halftime) will make a comeback? What is your best guess? Please take a moment to come up with your best sensible estimate before looking at the answer below.
Let’s dive into the numbers by referring to our huge dataset which contains information about all games from the past 14 NBA seasons (from season 2002/2003 to 2015/2016). The table below presents the numbers of wins-losses by the road team when it was trailing by “x” points after quarters 1, 2 and 3:
|
Home team’s lead |
Through quarter #1 |
Through quarter #2 |
Through quarter #3 |
|
1 |
356-546 (39.5%) |
281-377 (42.7%) |
231-340 (40.5%) |
|
2 |
356-552 (39.2%) |
258-425 (37.8%) |
200-360 (35.7%) |
|
3 |
301-572 (34.5%) |
231-426 (35.2%) |
180-374 (32.5%) |
|
4 |
225-547 (29.1%) |
219-455 (32.5%) |
145-410 (26.1%) |
|
5 |
211-584 (26.5%) |
182-452 (28.7%) |
132-425 (23.7%) |
|
6 |
215-514 (29.5%) |
165-449 (26.9%) |
133-441 (23.2%) |
|
7 |
159-505 (23.9%) |
131-474 (21.7%) |
100-441 (18.5%) |
|
8 |
138-435 (24.1%) |
117-424 (21.6%) |
76-435 (14.9%) |
|
9 |
113-405 (21.8%) |
88-440 (16.7%) |
54-430 (11.2%) |
|
10 |
79-359 (18.0%) |
71-459 (13.4%) |
52-417 (11.1%) |
|
11 |
52-314 (14.2%) |
73-401 (15.4%) |
37-418 (8.1%) |
|
12 |
59-241 (19.7%) |
41-327 (11.1%) |
17-374 (4.3%) |
|
13 |
46-225 (17.0%) |
22-337 (6.1%) |
15-340 (4.2%) |
|
14 |
19-175 (9.8%) |
29-277 (9.5%) |
8-318 (2.5%) |
|
15 |
18-147 (10.9%) |
25-240 (9.4%) |
8-321 (2.4%) |
|
16 |
14-111 (11.2%) |
17-185 (8.4%) |
8-291 (2.7%) |
|
17 |
6-88 (6.4%) |
9-201 (4.3%) |
4-254 (1.6%) |
|
18 |
5-72 (6.5%) |
11-194 (5.4%) |
2-235 (0.8%) |
|
19 |
4-48 (7.7%) |
9-167 (5.1%) |
1-220 (0.5%) |
|
20 |
1-31 (3.1%) |
2-109 (1.8%) |
1-201 (0.5%) |
Based on the numbers from this table, the answer to our previous question is: a road team trailing by 3 points at halftime has approximately a 35.2% chance of coming back to win the game. Was your best-guess close? Most people tend to overestimate that figure (a lot of fans will come up with a number that is in the 40%-45% range). If you guessed right, congratulations!
We expect the winning percentages to decrease as we move down a certain column (i.e. for a given quarter). In other words, the more the home team’s lead is big, the more the road comeback probability should be small. As you can see, it does generally decrease, but there are exceptions due to small sample sizes. The same concept applies when moving from left to right on a given row: the possibility of a comeback decreases after three quarters compared to the same lead after two quarters, for instance.
Have you ever had thoughts of betting your house on a home team leading by 20 points after quarter #3? Think again. While it may look like an impossible feat to accomplish, the numbers in the above table show that one road team did overcome a 20-point deficit after three quarters, while 201 teams failed. The only team to do it over the past 14 seasons is the Seattle SuperSonics on April 7th, 2007. And they did not even need overtime to do it! Trailing 87-67 after three quarters in Utah, they staged a furious comeback by outscoring the Jazz 39-16 in the 4th quarter, thus winning by a 106-103 score. I’m sure the 19,911 stunned fans at EnergySolutions Arena still remember that game.
We observe a similar pattern when the home team led by exactly 19 points through three quarters. Only one time out of 221 occasions did the road team manage to win the game in such a situation (over the past 14 NBA seasons). The only exception occurred on December 21st, 2009 when the Sacramento Kings beat the Chicago Bulls 102-98 after trailing 88-69 after three quarters. Want to hear something even more amazing? At one point during the 3rd quarter, the Kings actually trailed by as much as 35 points!
How about the home team’s comeback probabilities? Again, let’s look at the numbers from the past 14 NBA seasons:
|
Road team’s lead |
Through quarter #1 |
Through quarter #2 |
Through quarter #3 |
|
1 |
486-324 (60.0%) |
391-296 (56.9%) |
278-282 (49.6%) |
|
2 |
451-421 (51.7%) |
318-273 (53.8%) |
231-276 (45.6%) |
|
3 |
378-377 (50.1%) |
301-299 (50.2%) |
218-293 (42.7%) |
|
4 |
325-392 (45.3%) |
244-276 (46.9%) |
172-307 (35.9%) |
|
5 |
256-361 (41.5%) |
210-317 (39.8%) |
133-305 (30.4%) |
|
6 |
250-353 (41.5%) |
190-329 (36.6%) |
124-304 (29.0%) |
|
7 |
218-307 (41.5%) |
154-283 (35.2%) |
94-312 (23.2%) |
|
8 |
180-274 (39.6%) |
129-298 (30.2%) |
77-310 (19.9%) |
|
9 |
118-239 (33.1%) |
100-262 (27.6%) |
48-277 (14.8%) |
|
10 |
103-186 (35.6%) |
79-254 (23.7%) |
39-263 (12.9%) |
|
11 |
69-189 (26.7%) |
75-223 (25.2%) |
38-246 (13.4%) |
|
12 |
63-137 (31.5%) |
54-204 (20.9%) |
14-227 (5.8%) |
|
13 |
45-108 (29.4%) |
36-185 (16.3%) |
11-196 (5.3%) |
|
14 |
20-100 (16.7%) |
33-192 (14.7%) |
12-182 (6.2%) |
|
15 |
22-76 (22.4%) |
23-129 (15.1%) |
10-177 (5.3%) |
|
16 |
17-54 (23.9%) |
15-108 (12.2%) |
6-161 (3.6%) |
|
17 |
10-45 (18.2%) |
9-101 (8.2%) |
6-119 (4.8%) |
|
18 |
5-29 (14.7%) |
8-94 (7.8%) |
2-134 (1.5%) |
|
19 |
6-18 (25.0%) |
7-82 (7.9%) |
2-117 (1.7%) |
|
20 |
3-13 (18.8%) |
4-43 (8.5%) |
1-81 (1.2%) |
There are huge differences between the numbers in the two tables (corresponding to road and home comeback probabilities, respectively)! For example, let’s look at the case of a 1-point lead through one quarter. A home team in such a deficit still has a 60.0% chance of winning, whereas a road team with the exact same 1-point deficit only has a 39.5% chance of beating their opponents. There are several cases where we find a 10% difference or more (up to 20%, like the example above).
It is interesting to note that the home team still has more than a 50% chance of winning despite trailing by as much as 3 points after 1 or 2 quarters of play. However, any deficit through 3 quarters leads to a less than 50% comeback probability. Also, home fans should not lose hope when their team trails by as much as 12 points after the 1st quarter: according to the numbers above, they still hold more than a 30% chance of prevailing! Trailing by 11 points after 3 quarters? Don’t throw in the towel yet, your home team still has a 13% chance of making you happy!
Now, we can dig even deeper in order to come up with more accurate numbers. Recall our very first example: a road team down by 3 points through quarter #2. We saw earlier that such a team has roughly a 35.2% chance of making a comeback to eventually win the game. However, things are very different whether we speak about a team that was a huge favorite coming into the game, versus a team that was already established as an underdog by bookmakers prior to the match. In other words, the pregame spread (or “pregame line”) has a big impact, and needs to be taken into account.
Following that advice, we break things down into 4 categories:
- Big road favorite (if road team was favored by 7 points or more)
- Small road favorite (if road team was favored by 0.5 – 6.5 points, or pick’em)
- Small road dog (if home team was favored by 0.5 – 6.5 points)
- Big road dog (if home team was favored by 7 points or more)
As suspected, the comeback probabilities vary a lot from one category to the other. In our 3-point road deficit example, the big road favorite has a 62% chance of winning, the small road favorite 49%, the small road underdog 38% and the big road underdog 16%.
Remember that huge SuperSonics comeback we told you about earlier? What’s even more astonishing is they were actually big underdogs, as the Jazz were 9-point favorites prior to the game. As for the other big comeback mentioned previously, Sacramento came back despite being 4.5-point underdogs to Chicago. Quite impressive as well!
When you sign up for our service at www.basketball-live-betting.com, we provide live probabilities that are extremely game-specific. More precisely, we look at games from the past 14 NBA seasons that had the same pregame spread (± 1 at most) and the same current score (±1 point at most). We then compare what has happened in those games with the current live in-play spread (“live in-play line”) to estimate the probability of winning a bet on the road/home team. You simply cannot get data that is more relevant than this when considering NBA live betting!