Friday, August 28, 2009

World Cup Qualification - CONCACAF

How It Works

After 3 preliminary rounds, the final round (where we are now) follows a league format with six teams, commonly referred to as the hex. All teams play each other twice, once in each country. As usual, three points are given for a win, one for a draw and none for a loss. The top three teams advance to the World Cup finals in South Africa. The fourth-place team has a playoff with the fifth-place team from CONMEBOL (South America).

Breaking Ties

Should teams be equal on points, the first two tie breakers are goal difference (goals scored minus goals conceded) and goals scored in all matches. If two or more teams have the same points, goal difference and goals scored then they are sorted by points and if necessary goal difference and then goals scored restricting attention only to matches involving those teams.

Where the Group Is Now

The current table, with all teams having played 6 out of 10 matches, looks like this:

Costa Rica are two points clear at the top with 12 points, Honduras and the USA are even with 10, Mexico have 9 and El Salvador and Trinidad and Tobago have some work to do with 5 points each. Each team has played every other team at least once. Curiously, the top pair of teams, the middle two teams and bottom two teams have played each other twice so broadly speaking the schedule favors the teams at the top.

The first thing that jumps out at me is that there is a lot more parity than usual. Only 7 points separate the top team in the group from the bottom and you can't really argue that one or two teams are dominating. For comparison, here is the table this many matches into qualifying for Germany 2006:

(note: I'm using the current tiebreakers, which are different than 2006. In 2006, Costa Rica were ahead of Guatemala because they beat Guatemala in their only meeting to that point)

Four years ago the US and Mexico dominated the hex. At this stage, the US had lost 2-1 to Mexico in Azteca but won their other 5 matches. Including the win over the US, Mexico won 5 out of their first 6 matches and got a draw in the other. Oddly enough, Mexico's only blemish was against Panama, by far the weakest team in the group. They were terrible and went on to lose their last four matches finishing with two draws and eight losses in the final qualifying round. This year there are no teams that have gotten similar results to Mexico, the US or, at the other end of the spectrum, Panama four years ago. Only 7 points separate the top and bottom compared to 14 points last time around at this stage. Panama was effectively eliminated four years ago. While it isn't likely that either goes through (see below), it's certainly possible for El Salvador or Trinidad and Tobago to make it. At the top, the US and Mexico were so dominant in qualification for the 2006 finals that if you kept the 2-0 win over Mexico by the US that would come later and gave both of them a one-goal loss in all of their other remaining matches then both teams still would have gone through! This year even Costa Rica at the top of the table aren't completely safe.

Looking not at the table but the results, another thing that sticks out is that playing at home has been huge. Thus far in the final round, the home team has won 14 matches, drawn 3 and only once has the away team gotten a win. That honor belongs to Costa Rica for their 2-3 win over Trinidad and Tobago. This means that home teams are averaging an astounding 2.5 points per match with away teams eeking out a scant one-third of a point. This again is different from qualifying for the 2006 finals. Then home teams went 20-4-6 (W-D-L) and averaged 2.13 points per match while away teams averaged 0.73 points in their matches. Naturally, scoring follows a similar pattern. A total of 37 goals have been scored by home teams and 14 by the visitors. That averages out to 2.06 goals for the home team and 0.78 for the away team. Four years ago, home teams scored at a rate of 1.9 goals per game and conceded 0.87. This goes hand in hand with the previous paragraph - weaker teams have been much better able this time around to get good results even against stronger teams, especially at home.

Poisson Predictions

I plugged all the results from the current CONCACAF World Cup qualifying campaign into the Poisson model. Using these results it comes up with a scoring and conceding stat for each team as well as a number that represents the benefit of playing at home. These can be used to simulate results for matches that haven't taken place to determine the likelihood of qualification for each team. In the next article, I will discuss adding in results from the 2007 and 2009 Gold Cups. Doing this changes the predictions and I don't want to muddy this article with that discussion.

Based only on 2010 qualifying results, here is a chart giving the percentage chance of advancing for each team.

The first numbered column gives the percentage chance of qualifying by being in the top 3 of the group. For example, it indicates that the US has about an 83% chance of finishing in first, second or third in the group. Finishing in the top three automatically sends a team to South Africa next summer. The next column gives the percentage chance of finishing in fourth place. Finishing there forces the team to win a playoff against the fifth-place team from South America. The last column is the chance that the team finishes in fifth or sixth, completely eliminating them from the competition.

Here is a quick breakdown for each team.

Costa Rica

The ticos have performed well and find themselves in great shape three points clear of Mexico in fourth place. According to the model they are the best attacking team but second-worst defensively in the hex. It would take a fair collapse to fall out of the top three and finishing in the bottom two is extremely unlikely. I give them about a 90% chance to finish in the top three and a 10% chance of finishing fourth putting their chance of qualification in the 94-95% range. The key for their next match, September 5th at home against Mexico, is not to lose. A Mexico win would put the two teams even on points, most likely a point behind both Honduras and the United States. If Costa Rica win then they are essentially in - they would have a 98% chance of a top-three finish according to the model. A draw is fine, but does decrease their chances to 84% of qualifying automatically and about a 15% chance of finishing in fourth. So their overall chances drop, but just a few percent. A home loss to Mexico on the other hand lowers their chances drastically - 64% for the top 3 and 34% for fourth. That means roughly an 80% shot of making it to South Africa, a drop in likelihood of about 15%. Preventing Mexico from gaining on them is pretty important here.


Honduras just edges out the US as the second-most-likely team from CONCACAF to reach the World Cup finals. According to the model they are the best team defensively and third best at scoring. They have about an 84% chance of finishing in the top three and a 15% chance of finishing fourth for roughly a 90-91% chance of making it to South Africa. Their next match is against Trinidad and Tobago at home. There aren't many great chances to get three points and this is pretty easily their best shot to do so in their last four matches. Their odds reflect this: if they win then they go through in the top three 88% of the time, while a draw lowers this to 70%. If they somehow lose then their chance of a top-3 finish falls all the way to 57%. The schedule probably adds even more importance to getting a win than the Poisson model suggests. If they just get a draw on September 5th against T&T then four days later they will go into Azteca stadium at most two points clear and possibly in fourth place if Mexico manage a win in San Jose. It's tough enough to play in Mexico City as it is, but going in feeling like you need a result is a very tough task.

United States

The model has the US as the second-best team at both scoring and defending. While the results have not been as strong as usual, the Americans find themselves in great position to go through with about an 83% chance of qualifying automatically and a 15% chance of finishing fourth and playing against a South American team for a spot. Like Honduras, that means they have around a 90 or 91% chance to play in South Africa next summer. The similarities with Honduras don’t end there. The next US match is September 5th against El Salvador in Utah. It is vital that they do not squander their best remaining opportunity for three points. A win against El Salvador puts them at 90% to finish in the top 3 with the other 10% being their chances of finishing fourth - about a 95% chance of qualifying. Getting just a point drops the US to a 71% chance of a top 3 finish and a 27% chance of finishing fourth - about an 84% chance of making it to South Africa for a drop of over 10 percent. A loss would not only be embarrassing but it would lower the Americans' chances to 56% for a top 3 finish and 34% of finishing fourth - good for roughly a 72% chance of reaching the finals. In other words, a win and they are in fantastic shape and anything less leaves things a bit murky. On September 9th they travel to Trinidad and Tobago, a match that is also winnable. With a win against El Salvador, the US should be able to pretty much wrap things up with a win in Port of Spain.

Given the US-Mexico rivalry, a natural question is how much of a blow the 2-1 loss to Mexico was. The answer is not all that much - it cost them about 12% equity for a top 3 finish and a little under 7% overall. In other words, the model currently predicts that the US will qualify automatically 83.3% of the time and finish in fourth 15% for about a 91% chance to qualify. Had the US held on for the 1-1 draw they would be sitting pretty with a 95.7% chance of a top-three finish and a 4% chance of finishing fourth for a qualification percentage of roughly 98%. The difference between the two is 12.4% for automatic qualification and 7% overall. Giving Mexico 3 points pulled them that much closer, making it a fair bit more likely that they finish over the US, forcing the Americans to play against a South American team for qualification. Even so, the US is still in great shape to finish in the top 3 and will most likely finish above Mexico so it wasn’t all that important.


Mexico have been pretty disappointing by historical standards and downright mediocre in their qualifying matches. They rate as the fourth best team in both attacking and defending. They narrowly beat Trinidad and Tobago 2-1 at home, lost at El Salvador 2-1 and lost by two goals away against both Honduras (3-1) and the United States (2-0). Despite these lackluster results, they find themselves in decent shape to qualify - although they likely will need to best the fifth-place South American team to do so. The model claims that they have a 41% chance of finishing in the top 3 and a 50% chance of finishing fourth. That puts them somewhere around 65% to make it to South Africa. Getting a result in their match on September 5th at Costa Rica would be quite beneficial. If they get a draw then their chance of a top-3 finish goes up to 47% and their overall chance of making it goes up 5% to 70%. A loss on the other hand drops them to a 29.5% shot at automatic qualification and about 58.5% overall. Should they get a win then they are in great shape with a 78% chance of a top-3 finish and about an 88% chance overall. It is a key match at this stage and given likely wins by the US and Honduras, a loss by Mexico would put them 4 points out of third place. There isn’t a lot of room for them to slip up, and they most likely will have to win out if they lose in San Jose.

The win over the US was a lot more important to Mexico than the loss was for the US. Had they failed to break the 1-1 deadlock, they would have only about a 17% chance of a top 3 finish to go with a 60% chance of finishing fourth. Giving them even odds to win in a playoff that would put them at a 47% chance to make it. With the win against the US they increased their chances to about 41% to go through automatically and 50% of a playoff for a 66% chance of qualifying overall. In short, getting all three points against the US made Mexico about 24% more likely to qualify automatically and 19% more overall. So you could say that while the loss wasn't very bad for the US, they missed out on a great opportunity to seriously damage Mexico's chances by not getting a draw.

El Salvador and Trinidad and Tobago

I'll cover them together because they are in very similar situations. Both are really up against it. It would definitely be a surprise if either made it, but stranger things have happened. Both have about a 1% chance of finishing in the top 3. El Salvador is rated a bit higher with close to a 7% chance of finishing fourth while the islanders are looking at just under 4%. Given that both would be significant underdogs in a playoff against the 5th South American team, I'd say each of these teams qualifies two or three times out of a hundred. El Salvador plays at the United States while Trinidad and Tobago plays at Honduras. If either can somehow get an upset win they would increase their chance of qualification to close to 15%. On the other hand if they get the expected result and lose then their already slim chances would be cut in half.


We essentially have the top 4 teams battling it out to determine which three go through to the finals automatically with the odd-man out forced to play a home-and-home with a South American team. Based on the results of this qualification round, Mexico is the favorite for that fourth spot, getting it about half the time. The next matchday is very important for all four teams, with Mexico traveling to Costa Rica and the US and Honduras playing weak opponents at home. If Mexico can manage a win or the US and/or Honduras fail to win then things will change fairly drastically.

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