I was talking to a friend yesterday about the differences between sports betting in the US and in the UK. As an example in the conversation I pulled up the odds for the Everton-Arsenal match for this weekend and I was surprised to learn that Everton are the bookmakers favorites to win the match: 40% Everton win, 30% draw, 32% Arsenal win.
I have to admit that I don’t gamble on sports. I don’t know why, other than it seems like gambling on sports would ruin sports for me. I’ll have a flutter every once in a while, but nothing serious, which would require me to build a model to find value in the Premier League market.
That latter bit would be the part that ruined sport because then I would have to see my favorite team as just another data point in the model rather than as some romantic metaphor.
But the bookmakers don’t mess around. The fact is that Everton have been favorites in this fixture now for two years and by basically the same margin. And in this same fixture last year you might remember that Arsenal were lucky to escape with a point.
Despite dominating the possession stats, Arsenal found it very hard to break down Everton’s defenses and only managed 3 shots on target. That includes Theo Walcott’s 1st minute goal which set Arsenal up for the draw. Meanwhile, Marouane Fellaini dominated the Arsenal midfield and as a result, Everton created 9 shots on target. That game also featured a poor clearance by Sagna which led to the Fellaini goal, a brash tackle by Gibson which I think should have seen him off, and a lucky escape by Arteta for a tackle on Pienaar in the box. It was a game that in many ways mirrored some of our worst performances of the season: sterile domination and an error prone defense.
From a sports-writer’s perspective it’s easy to tell why Arsenal aren’t favorites in this game: injuries and recent form.
Even with the great news that Aaron Ramsey is on his way back, you have to admit that Arsenal’s injured list reads like a who’s who of Arsenal starters: Walcott, Wilshere, Koscielny, Ramsey, oh and Özil. Meanwhile, Everton look almost certain to recover Phil Jagielka and Ross Barkley for this match. Add to that the fact that all their regular starters, like Romelu Lukaku (who has scored 4 goals in the 8 appearances since his return from injury), and you can see that Everton are significantly healthier than Arsenal at the moment.
Recent form favors the blues as well. In League play, Arsenal have won just 3 of their last 10 matches, going 3-4-3 and taking just 13 points from a possible 30. Everton, on the other hand, are on a 5-match winning streak and have a 6-1-3 record in the last 10 games. Those three losses were all to top seven teams (Liverpool, Chelsea, Tottenham) but they were also all away games.
And head to head, home record v. away record, again favors the Toffees. Everton are 11-3-1 at home, losing just once to Sunderland (0-1) and drawing to Tottenham (0-0) and Liverpool (3-3). However, what is keeping the bookies’ odds close is the fact that Arsenal have the second best away record (29/48 points) and 4th best goal scoring record in away games (27 goals scored).
You could, however, simplify all of these arguments and just look at goal difference. In their seminal work Fitness, chance, and myths: an objective view on soccer results Heuer and Rubner lay out a compelling argument for why goal difference is the key stat for determining the relative strength of a team. This is something I have felt was true for a long time but never put the work in to prove it. Again, using goal difference, you can see why Everton are favorites. Despite their rather good record in terms of both results and goals scored, Arsenal’s away goal difference over the last three seasons has been just +14 (it is +/-0 this season) while our overall goal difference has been +79. And that figure is largely buoyed by Arsenal’s best-in-the-league away defense last season where we only allowed 14 total goals.
This season is another odd one. The Gunners have scored 27 away goals and have conceded 27 for a 0 GD. However, as you know, 17 of those 27 goals came in just three games. If we abstract those big losses out, Arsenal’s away record goes from one of the worst in the League to the best in the country, scoring 23 and conceding a measly 10 in 13 games. In fact, if we take out the big away losses in 2011-2012 (against Man U and Blackburn) Arsenal go from having the 11th worst away defense to the 3rd best. So, without the five big losses in away games the last three years, Arsenal actually have a pretty solid away defense conceding just 44 goals in 51 games but 29 goals in those five games. mentioned above. I guess when Arsenal lose they really are the best at losing!
If there is any “value”* to be found in the stats above it’s that Arsenal’s away record is so strange over the last three years that you might take pause. On the one hand, Arsenal have the most consistent, stingiest away defense in the League over the last three years. On the other hand, Arsenal also have allowed 29 goals in just 5 games.
Can Arsenal get a win in these circumstances or are the odds-makers right?
*The difference between the odds on offer and the probability of a result going in favor of the gambler.