With the disapointment of the 2008 Champions League Final behind them, Chelsea can finally claim to be the best team in Europe. As in 2008 it was decided by another penalty shoot but this time Chelsea were the victors. As always I am particularly interested in the peanlty shoot out and the strategies, if any, that are implemented by both the penalty taker and the goalkeeper.
The situation that kickers face in a penalty kick is a simultaneous-move game where they have three alternative strategies: shooting right, left, or centre. Similarly the goalkeeper also has three alternative strategies: dive to the right, dive to the left or remaining in the centre of the goal. In defining the sides of the goal researchers use the “natural side” of the kicker (which is the goalkeeper’s right, if the kicker is right-footed, and the goalkeeper’s left, if the kicker is left-footed) and the “opposite side”. Labeled like that, the strategies of both kicker and goalkeeper will be to choose the natural side of the kicker (NS), the centre (C) or the opposite side (OS).
From data compiled by Spanish economist Ignacio Palacios-Huerta he calculated the proportion of successful penalty kicks. Below is a table that shows the success rate of penalty takers when they went to their natural side and opposite side when the goalkeeper went his natural side and opposite side. Notice that when the kicker went NS and goalkeeper OS the success rates was 95% – the remaining 5% missed the target. Similarly when the kicker went OS and goalkeeper went NS – 8% missed the target.
Here is data on the peanlty kicks from last Sunday’s Champions League final
Notice that Chelsea keeper Petr Cech went the correct way for all penalties (including the one taken during normal time) – seemingly on the plane over he studied all Bayern penalties since 2007. He said it took nearly 2 hours – did he have a strategy?
Also Chelsea penalty takers favoured the natural side whilst Bayern the opposite side. Below is the shoot out once again.