Comparing offensive and defensive dominance in the CFL from 1980 to 2015

Mark Fulton has been doing some great statistical analysis of the CFL lately, and something he came up with earlier this week deserves further examination. Fulton crunched the numbers for the 1980 to 2015 CFL seasons to see if the "defence wins championships" adage is correct, and his results suggest it really isn't in this league:

Let's take a look at larger versions of those graphs and break down what's going on in them. Here's the first one:

So, 44.44 per cent of the teams that won those Grey Cups didn't lead the league in the regular season in either points for or points against, and 16.67 per cent led the league in both categories. Neither of those stats is particularly helpful for a comparison of offensive dominance versus defensive dominance, but the other two segments here are: 22.22 per cent of the champions were teams that led the CFL in points for during the regular season, while only 16.67 per cent were teams that had the best defence by points against. We're looking at 36 total champions here, so we can convert these percentages into numbers of teams by multiplying them by 36.

Thus, there were eight champions who led the regular season in points for, six who led in points against, six who led in both, and 16 who didn't lead in either category. Two more teams that were tops on offence alone won than teams who were tops on defence alone, which isn't necessarily huge, but it does suggest there may be something here. Here's a year-by-year look at when Grey Cup champion teams led the league in offence, defence, both or neither.

Those charts are about stats relative to the rest of the league, though. What about stats relative to the Grey Cup opponent? That's what Fulton's second graph looks at:

Here, there isn't really a clear conclusion (other than it's really nice to be better than your opponent in both categories, as 18 of the 36 teams were). Six teams with the better offence won, six teams with the better defence won, and six teams with neither won. So, this one doesn't suggest that offence is more important than defence, but it does help disprove the idea that defence is always more important.

There are challenges with drawing these kinds of comparisons across decades, though, as the CFL game has changed incredibly over the years. Consider how rushing attempts per game fell by almost half from the CFL's beginnings in the 1950s to the early 2010s. Similarly, offensive and defensive schemes have changed substantially over the 1980-2015 data set in question here. Also, a very defence-focused team in Edmonton just won the Grey Cup: does that mean defence is on the rise?. Let's consider the last five Grey Cup winners and how they stacked up against their opposition. Here's what 55-Yard Line research on that suggests:

So, by Fulton's second graph, there's no real further insight here; we have four champions that won both categories and one that lost both. By the criteria of his first graph, though, this is more interesting: three of the last five Grey Cup winners had the league's best defence, while only one had the best offence, none had both, and one had neither. Thus, there may well be a bit of a recent movement towards defence.

There are a few things to keep in mind here, though. First off, five years is a relatively small sample size, so this might not be an actual trend. Moreover, all of these teams but the 2012 Toronto Argonauts had great regular-season offences in addition to their defence, even if the 2014 Calgary Stampeders were the only one to top the league. Meanwhile, that Calgary team also had a tremendous defence. Perhaps the even more interesting insight from the last five years of data is that one team (in every case, the West team) has been clearly ahead in both categories each year, and that team has won four times out of the five times.

Keep in mind how this data can be affected, too. The 2012 Argonauts look like a bad team by the season-long stats, but that's thanks to some of the early issues they had integrating a new quarterback and coach and drastically changing their offence. They were clicking by the playoffs, and much closer to Calgary's level than the season-long stats showed. Similarly, the 2014 Tiger-Cats got off to a rough start thanks to large amounts of personnel turnover, but really poured it on down the stretch, and that Grey Cup was a very close one. So, season-long data isn't always indicative of how things work by Grey Cup time. Another thing to keep in mind that the points here (for and against) are total points, so defensive and special teams scoring (both for and against a team) can also affect this. Ottawa's offence actually produced more points than Edmonton's last year, but the Eskimos had more total points, so they win that category here. (Points by offence data would be better, but that wasn't included in the CFL year-end stat sheets before this past season.)

Overall, though, having either a great offence or a great defence seems to be an excellent recipe for winning the Grey Cup, and being ahead of your opponent in either or both categories helps too. Having the league's best offence seems slightly better over the last 36 years, while having the league's best defence seems better over the last five. Fulton's premise that "defence wins championships" isn't always true certainly holds up, though. It can, but a superb offence certainly can as well.