Were Chelsea right to change goalkeepers for penalty shootout in EFL Cup final?

There is a good reason and a bad reason for substituting goalkeepers for a penalty shootout.

The good reason is that you have a reasonably large sample of data on the penalty-taking habits of several opposing players and you think the goalkeeper sitting on the bench is more likely to absorb it and remember it than the goalkeeper who has played for 120 minutes.

Many players have a favourite penalty-taking style and direction, and knowing it may help a goalkeeper. Knowing it may have helped Tim Krul when the Netherlands brought him on for a shootout against Costa Rica in the 2014 World Cup quarter-finals. Netherlands had a history of analysing the penalty-taking choices of opponents. Krul saved two penalties out of five and Netherlands won the shootout 4-3.

The bad reason for swapping keepers for a shootout is that up until now your second-choice keeper has saved a higher proportion of the penalties they have faced than your first-choice keeper. Those sorts of differences tend to occur randomly and be meaningless as a guide to what will happen next.

Chelsea replaced Edouard Mendy with Kepa Arrizabalaga for a penalty shootout against Liverpool in the EFL Cup final on Sunday. Chelsea manager Thomas Tuchel said afterwards that Kepa had a slightly better past record of saving penalties. Kepa did not save any of the 11 penalties Liverpool took then missed his own. Chelsea lost the shootout 11-10.

Liverpool goalkeeper Caoimhin Kelleher, it should be added, did not save any of the penalties he faced – ten went in and one went over. Mendy may or may not have stopped some of the shots Kepa could not.

Chelsea also replaced Mendy with Arrizabalaga last August for a shootout in the Uefa Super Cup against Villarrreal. Then Kepa saved two penalties out of seven and Chelsea won the shootout 6-5.

Before last Sunday Kepa had kept goal for Chelsea in seven shootouts. Altogether 32 kicks from opponents were on target and Kepa saved seven of them – 22 per cent. That was a fairly ordinary stopping-rate.

The Economist analysed nearly 3,000 penalties taken over ten seasons in the Premier League, La Liga and Bundesliga. These were spot-kicks taken during league fixtures, not in shootouts to decide knockout ties. The Economist said: “We have found no statistically significant relationship between a player’s past conversion rate and his future success. This does not mean that each penalty is a total lottery. But it does suggest that any edge a skilful finisher might have is too small to be detected, given how infrequently penalty kicks occur.”

To give a specific example of the general point they were making The Economist chose Lionel Messi when he was at Barcelona. In La Liga 77 per cent of all penalties were scored. Messi scored 93 per cent of his first 27 penalties then 78 per cent of his next 27 penalties. The full figures were 25 of the first 27 then 21 of the next 27.

If penalties scored, saved and missed during past games – rather than how they were approached and where they were aimed – gives no indication of what will happen during future games it is reasonable to suggest that the same is probably true for penalties taken in shootouts. True for kickers and true for keepers.

What are the odds of such a long drama?

The first 21 penalties in the shootout between Chelsea and Liverpool were scored. What was the chance of that happening?

Here is a rough suggestion.

The conversion-rate for penalties varies depending on where you look and when. It tends to be between 75 and 80 per cent.

If there was an 80 per cent chance of each penalty being scored the odds against 21 in a row all going in would be just over 100-1. If there was a 75 per cent chance of each penalty being scored the odds against 21 in a row all going in would be more than 400-1.

My best guess would be between those odds, but a lot closer to the higher ones. Penalties can be higher-pressure in shootouts than in normal or extra time, and if they keep going in eventually everyone has to take one, whether they want to or not, whether they normally would or not.

Odds around 400-1 are large but shootouts occur reasonably often. Last May there was a shootout in the Europa League final between Villarreal and Manchester United like the one on Sunday in the EFL Cup final between Chelsea and Liverpool. The first 21 penalties were scored, the last of those by a goalkeeper, then the other goalkeeper did not score.

Leeds are the best argument against criticism of Leeds

Insanity is doing the same thing over and over and expecting different results.

I found those words in an article on the BBC website last Saturday after Leeds had lost 4-0 at home to Tottenham in the Premier League. The quote was one in a section at the bottom about reactions on social media.

The main body of the article said Bielsa’s job was in jeopardy, which proved right. He was sacked on Sunday.

“Insanity is doing the same thing over and over and expecting different results.” Those are words that sound like they must be true.

If we were talking about something mechanical they probably would be true. If you go to the top of a tall building and drop a stone over the side it will fall to the ground. No matter how many times you do this the outcome will always be the same.

But when we are dealing with living things it is not unusual for the same action to be followed at different times by different outcomes.

A good example of this are … Leeds.

Everyone agrees that Bielsa never changes. He always gets his teams to play the same way, no matter what. Leeds played the Bielsa way last season and got good results. They played the Bielsa way this season and got bad results. Leeds are a perfect example of how a football team can do the same thing over and over and get different results.

Another quote from social media seemed to recognise this. “The people moaning about Leeds and Bielsa are probably the same people who celebrated the excitement Leeds brought to the Premier League last season. We’ve never seen anything as crazy as this Leeds team in the Premier League, I pray they cling on to 17th and don’t change a thing.” Now we will never find out whether Bielsa’s Leeds would have survived.

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