How important is winning a World cup group? Do the best teams win their groups? Can group form be a good predictor of knockout stage success? Read on to find out.
How important is winning the group?
At first glance winning the group is very important. Group winners are more likely to progress beyond the Round of 16 with 31 of the 40 group winners managing to do so compared to just nine runners-up.
The average group winner wins a total of 1.575 World Cup knockout matches compared to just 0.325 elimination matches won by the average runner-up.
However, this is not necessarily a fair test. If we assume that the group winners are stronger on average than the runners-up then inferior group winners could be progressing through merely playing weaker qualifiers who failed to win their group. Can we assume that the best teams in the tournament won their groups?
Do the best teams win their groups?
Wins in the knockout stage are a useful way to measure the success of a team as the tournament progresses.
To see if the group winners were truly more successful over the course of the competition it is useful to remove the mismatches created by the way first place finishers are paired with runners-up in the round of 16.
To do this we can look at the number of matches won by each set of teams from the quarterfinals onwards.
As expected only nine group runners-up progressed beyond the first knockout round compared to 31 of the group winners.
After winning their round of 16
Second place finishers who progressed to the quarterfinal stage actually had an inferior goal difference to those who did not advance
It is clear that group winners are not only more likely to progress beyond the round of 16 but are also more successful from the quarterfinal stage onwards.
Even after negotiating the hurdle of a round of 16 match against a group winner the runners-up still possess an inferior record. Why could that be?
One explanation is that luck of the draw seems to play a bigger part for group runners-up. The defeated group winners progressed from the group stage with an average goal difference of 2.55 whilst the group winners who won one or more knockout games possessed an average goal difference of 4.87. Perhaps the defeated group winners were, in general, weaker qualifiers.
This demonstrates that the runners-up who make it through the round of 16 stage are not necessarily stronger than those who were eliminated since they defeated group winners that were, on average, weaker.
To back that up, goal difference does not correlate at all with which runners-up progress beyond the round of 16. Second place finishers who progressed to the quarterfinal stage actually had an inferior goal difference (+0.89 average) than those who did not advance (+1.125 goal difference).
Runners-up who outperformed group winners
On only five occasions in the last four tournaments have runners-up progressed further than the winners of their group. These are the five teams:
No runner-up has progressed further than winner of their group in the last two tournaments. It is notable that three of the five cases of this happening occurred during the 2002 World Cup, a tournament which saw an unusual number of surprise results and controversial refereeing decisions.
Of the more successful second-place finishers only Croatia made it beyond the quarter-final stage. This seems to underline the predictive quality of a first-place finish in the group stage
Making World Cup knockout stage predictions
As has been shown in this article, group winners win more matches and are more successful in the World Cup knockout stages than runners-up.
Interestingly, group stage form can also be used to predict which group winners are the most likely candidates to win the tournament.
Group winners who went on to win one or more knockout games had a 4.87 average group stage goal difference compared to a 2.74 average across all qualifiers for the knockout rounds.
The group winners who did not win a knockout stage game had an average group stage goal difference of just 2.55, suggesting they were below par teams who just happened to win a weak group.
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Perhaps it is best to avoid predicting success for teams who failed to dominate during the group stage, at least in terms of goal difference.
Additionally, it is evident how rare it is for runners-up to progress beyond the quarterfinals. In fact, just three of the 40 runners-up since France 1998 have progressed to the semi-final stage and none have made it to the final.
If bettors are looking for a team primed for success in the knockout stage then winning the group could be considered a prerequisite. It is also important to look out for teams with strong group stage goal differences as this metric correlates quite well with success.
When assessing runners-up goal difference is less useful. This could make sense since the stronger runners-up have emerged from a tougher group so it is important to look at the strength of their round of 16 opponents.
Conclusion and limitations
In conclusion, it seems group form is indeed a relatively good predictor of knockout stage success for group winners but runners-up are more reliant on a kind draw to progress. However, it is important to note that the sample size here is small.
With a restricted dataset to work from in 32 team tournaments, this may not apply perfectly to the 2018 World Cup but is certainly worth considering for bettors when predicting knockout stage success.