How important is the first goal?
One of the biggest problems I’ve experienced in evaluating the effect of performance variables on success is that it is difficult to establish how much these factors are truly influencing results.
For example, if there is a relationship between pass accuracy and winning, we might conclude that teams who pass well are more likely to win. But ask yourself this: if a team is winning, does that give the players more confidence to pass the ball better?
However, if there is a relationship between pass completion and scoring the first goal, it’s easier to suggest there’s a causal effect, particularly if we assume “goals change games”. First though, we need to determine how important the first goal is on the final result of a match. Infostrada Sports have provided me with the data to investigate.
Before reading on, it’s worth checking out Soccer Statistically’s excellent Outcome Probability Calculator, which gives you an idea of the effect of any goal in the Premier League. Mark Taylor’s The Power of Goals blog also looks at the impact of goals in certain matches, as well as examining the problems of drawing causal conclusions from football data.
Since the start of the 2007/08 season, teams who score first on average collect 2.25 points per game. This is fairly high; the immediate suggestion is that there is significant value in scoring the first goal in a Premier League match. The first goal is even more valuable at home.
Besides match location, the importance of the first goal will also vary on two other factors: the team who scored it and when it was scored. Clearly, late opening goals are more valuable, and this is supported by the data.
Curiously, goals in the 15 minutes before half time are more valuable, on average, than goals just after half time. Whilst this initially gives credence to the idea that scoring before the interval is particularly damaging to the opposition, it is statistically no different to scoring just after the break.
Stronger teams are also likely to convert leads into victories, though it can equally be said that teams who can do this will finish higher up the table.
Clubs in the top five positions on average earn a point when they concede the first goal; clubs in the bottom half tend to be teams who rarely respond well to going behind. To put expected points into perspective, 2.57 points per game corresponds to 98 points over the season, more than any title-winning team has ever achieved.
Some have argued the Premier League has become more unpredictable in recent seasons. The evidence from analysing first goals somewhat supports this, with scoring the first goal least valuable last season.
It’s no surprise, therefore, that out of the league’s top 10 teams in terms of expected points from scoring first (since 2007/08), only one side features from last season.
Remarkably, it’s not a title winner or even a European regular that can boast the best record after scoring the first goal – Harry Redknapp’s 2007/08 Portsmouth side converted every single one of their leads into victories. Interestingly, no title-winning teams feature in the top ten, though the league’s current top three are likely to change this come May. At the bottom, Derby could not even manage a draw on average after going ahead, a reflection of their horrid year in the top flight.
In terms of conceding first, no one has bounced back better than the Liverpool team of 2008/09, turning over 6 of 11 such matches into victories.
Derby again rank last of the 100 teams to have competed in the last 4 and a half seasons in the Premier League; they’re joined near the bottom by only three other teams who went down.
Understanding the value of the opening goal gives teams a simple, if obvious target. From here, as the Power of Goals points out, “the real question is how do teams take the lead and then how do they keep it.” It would be possible to analyse this through more disaggregated performance data; for example possession broken down by minutes. If teams (and fans) know how to best go about scoring the first goal, they’re onto a winner.
Data kindly provided by Infostrada Sports. You can follow them on Twitter @InfostradaLive.