Pro Football Reference Blog

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How often does the best team win?

Ten thousand seasons

Ten thousand seasons again

In the previous posts, I simulated ten thousand generic NFL seasons. In some of those seasons the "Seattle Seahawks" were great. In some they were terrible. In some they played a tough schedule, in others an easy one. In this post, I'll simulate ten thousand 2005 NFL seasons. The Seattle Seahawks will be a very good team in each of them, and they will play an easy schedule in each of them.

Mechanically, the procedures are similar, but philosophically there is a world of difference. The generic seasons had teams whose strengths I knew, so I could say things like "the best team" and "Chicago was not very good." I knew who the best team was and I knew how good Chicago was or wasn't. Exactly. Only because I knew those team strengths could I assign the proper probabilities to each game.

But if I want to simulate the 2005 season, I've got a problem: I don't know the team strengths. Neither do you. We have to guess. The guess I'm going to use is the team's rating from the simple rating system. I'm not going to spend time here making a case that that's the best guess or even necessarily a good guess. If you don't think the simple rating system is an adequate representation of team strength, that's fine. No hard feelings. But you'd better stop reading now, because that's the foundation this post rests on.

For those still with me, I'll make one more disclaimer. If I happen to say something like:

Seattle was the 4th-best team in football.

What I actually mean is:

According to the measurement of team strength that we have agreed upon --- which we acknowledge is imperfect in some obvious and some non-obvious ways --- Seattle appears to be the 4th-best team in football.

I am not trying to quash discussion of the merits of the various ways of estimating team strength and I am well aware of the weaknesses of the one I have chosen. But we've got to pick something and go with it, and the prose just seems to flow a bit better if you allow me to use the above shorthand notation. As you know, I can use all the help I can get with making the prose flow.

Now let's get to it. I'll just throw this summary out and then we'll discuss it.

Rating is the team's rating, which is my guess as to its true strength. Avg Wins is the average number of wins each team had over the course of the 10,000 seasons. Div is the number of division titles each team won. WC is the number of times each team got into the playoffs as a wildcard. PO = Div + WC. It is the number of times each team made the playoffs. SB is the number times each team made it to the Super Bowl and Champ is the number of times they won it.

TM      Rating  AvgWins    Div  WC   PO     SB  Champ

=====+=========+========+================+===========

ind  |   10.8  |  11.2  | 7128 1572 8700 | 2688 1640

sea  |    9.1  |  11.1  | 8936  395 9331 | 3461 1780

car  |    5.1  |  10.4  | 6304 1818 8122 | 1681  741

den  |   10.8  |  10.4  | 4342 2797 7139 | 1825 1092

pit  |    7.8  |  10.3  | 5741 1543 7284 | 1469  778

nyg  |    7.5  |  10.1  | 5083 2534 7617 | 1785  817

sdg  |    9.9  |   9.9  | 3190 2907 6097 | 1343  797

jax  |    4.8  |   9.6  | 2727 2951 5678 |  674  321

kan  |    7.0  |   9.4  | 2298 2842 5140 |  737  371

cin  |    3.8  |   9.3  | 3015 1974 4989 |  516  242

was  |    6.0  |   9.2  | 2986 2765 5751 |  989  416

chi  |    1.4  |   9.1  | 5653  793 6446 |  721  256

nwe  |    3.1  |   8.7  | 5001  476 5477 |  425  194

tam  |   -1.0  |   8.5  | 1969 2333 4302 |  315  103

dal  |    3.2  |   8.3  | 1552 2249 3801 |  409  166

atl  |   -1.2  |   8.2  | 1652 2122 3774 |  236   73

mia  |   -0.8  |   8.0  | 3385  481 3866 |  165   52

rav  |   -1.8  |   7.4  |  773  829 1602 |   61   22

min  |   -3.5  |   7.3  | 1864  774 2638 |  113   36

gnb  |   -3.7  |   7.1  | 1616  755 2371 |   93   29

ram  |   -5.1  |   6.9  |  528 1013 1541 |   59   10

cle  |   -4.2  |   6.8  |  471  518  989 |   32    9

crd  |   -5.0  |   6.7  |  481  884 1365 |   46    9

phi  |   -2.3  |   6.6  |  379  878 1257 |   61   16

rai  |   -2.8  |   6.3  |  170  427  597 |   22    9

det  |   -6.7  |   6.3  |  867  417 1284 |   27    6

buf  |   -5.8  |   6.2  |  889  179 1068 |   20    7

nyj  |   -6.4  |   6.0  |  725  136  861 |   18    6

oti  |   -7.6  |   5.8  |  108  256  364 |    4    2

htx  |  -10.0  |   5.1  |   37  112  149 |    1    0

nor  |  -11.1  |   4.9  |   75  139  214 |    4    0

sfo  |  -11.1  |   4.7  |   55  131  186 |    0    0

Indianapolis averaged 11.2 wins per season in the simulation. They won the AFC South 71.2 percent of the time, they made the playoffs 87% of the time, they made it to the Super Bowl about 27% of the time and won it 16.4% of the time.

If you were to translate this into an English sentence, it would not be: at the beginning of the season, we should have estimated that the Colts had a 16.4% chance of winning the Super Bowl. It would be something more like: knowing what we now know in hindsight about how good these teams were in 2005, if we were to play the season again with those strengths remaining the same, the Colts would have a 16.4% chance of winning the Super Bowl. Alright, that's pretty bad English but I hope you get the point.

The probability of winning the Super Bowl depends two things: the team's strength and their schedule (including the playoff schedule). You can see the effect of both in the table. Denver and Indianapolis were essentially equally strong, but the Colts' chances of winning the Super Bowl were significantly higher. And Seattle's were even higher, despite being a weaker team. Carolina had a title chance that was disproportionately high (compared to their true strength) and San Diego's was disproportionally low. We'll revisist them in a moment.

Also note that the spread on average wins --- from Indy's 10.8 to Houston's 4.7 --- is much smaller than the spread on actual wins in the 2005 season. This makes sense. I think it's safe to say that there is almost never an NFL team that is morally a 14-2 team or a 2-14 team. There are, though, probably three or four teams each year --- maybe more --- that are capable of going 14-2 if things break right for them, and there are another few that might slip to 2-14 if things don't. And the result is that we see 14-2 teams and 2-14 with some regularity. This idea might strike some people as controversial, but it's really no different from pointing out that no basketball player truly is a 50-point-per-game player even though certain players do score 50 from time to time.

OK, time to play god. Let's move the Chargers to the NFC South and the Panthers to the AFC West and see what happens.

TM      Rating  AvgWins    Div  WC   PO     SB  Champ

=====+=========+========+================+===========

sdg  |    9.9  |  11.7  | 8209 1158 9367 | 3344 1790

clt  |   10.8  |  11.3  | 7255 1615 8870 | 2881 1610

sea  |    9.1  |  11.1  | 8921  398 9319 | 2879 1520

den  |   10.8  |  10.6  | 5370 2328 7698 | 2134 1196

pit  |    7.8  |  10.4  | 5795 1684 7479 | 1563  787

nyg  |    7.5  |  10.1  | 5063 2508 7571 | 1478  727

jax  |    4.8  |   9.7  | 2592 3360 5952 |  731  317

kan  |    7.0  |   9.6  | 2980 2784 5764 |  902  441

was  |    6.0  |   9.3  | 3015 2879 5894 |  827  366

cin  |    3.8  |   9.3  | 2979 2222 5201 |  570  256

chi  |    1.4  |   9.0  | 5504  754 6258 |  522  184

nwe  |    3.1  |   8.7  | 4984  487 5471 |  476  195

car  |    5.1  |   8.5  | 1385 2076 3461 |  388  179

tam  |   -1.0  |   8.3  |  979 2862 3841 |  173   63

dal  |    3.2  |   8.3  | 1530 2287 3817 |  306  138

atl  |   -1.2  |   8.0  |  782 2516 3298 |  147   38

mia  |   -0.8  |   8.0  | 3298  551 3849 |  180   56

rav  |   -1.8  |   7.4  |  778  960 1738 |   62   23

min  |   -3.5  |   7.3  | 1933  661 2594 |   88   19

gnb  |   -3.7  |   7.0  | 1681  634 2315 |   86   22

ram  |   -5.1  |   6.9  |  559 1011 1570 |   36    6

cle  |   -4.2  |   6.8  |  448  593 1041 |   25    6

phi  |   -2.3  |   6.7  |  392  924 1316 |   49   19

crd  |   -5.0  |   6.6  |  458  793 1251 |   37   12

rai  |   -2.8  |   6.5  |  265  524  789 |   33   10

det  |   -6.7  |   6.3  |  882  369 1251 |   28    6

buf  |   -5.8  |   6.2  |  935  222 1157 |   32   10

nyj  |   -6.4  |   6.0  |  783  152  935 |   18    2

oti  |   -7.6  |   5.9  |  113  315  428 |    4    1

htx  |  -10.0  |   5.1  |   40  127  167 |    1    1

nor  |  -11.1  |   4.8  |   30  133  163 |    0    0

sfo  |  -11.1  |   4.7  |   62  113  175 |    0    0

Interesting.