The power of a local derby: do these games encourage better performance?

As part of our role as the official data and consulting partner of the United Rugby Championship (URC), our team will be getting together with Oval Insights, over the coming season, to break down some of the most exciting trends in the competition. Because we recognise the power of data insights on the pitch as well as in the boardroom…

Local derbies in the rugby world – there’s nothing quite like them.

The atmosphere, the emotion, the feeling of getting “one up” on your neighbours – there’s a reason why they are often some of the most-attended games in the calendar! The unique set-up of the URC, which has 5 countries involved, means that each season we are lucky to see several of these exciting matchups – some of the oldest rivalries in rugby. These games always feel close and fraught with tension.

We were discussing last weekend’s incredible Munster vs Leinster derby in the Elixirr offices this week, and it occurred to us – do teams “play up” to the rivalry at these games, and in turn improve their overall performance?

Likewise, because of the heightened emotion of the games, are players more likely to make significant errors (such as yellow/red cards), or can the occasion help in converting difficult penalties and conversions?

With Oval Insights’ help, we set about crunching the numbers to find out.

Test 1: Do teams perform better on average in derby games?

The parity of talent across the URC is impressive. In the last 2 years of the URC, we’ve seen 2 different champions – and this season alone, 5 different teams have topped the table after 6 rounds. Not only that, over 50% of games have provided losing bonus points, and only 6 points separate 3^rd from 11^th in the table at the time of writing.

We started testing our hypothesis by comparing the form of a selection of teams before their respective derby games. What emerged was an interesting trend:

6 out of 10 of our example derbies had been won by the team going into the game with the worst record. Of these, Scarlets vs Cardiff produced the biggest statistical upset: Scarlets had come into the game having lost 4 out of 5 previous games, whilst Cardiff had won 3 out of 5 in the same span. Despite playing away from home, Scarlets came away victorious in a 6-point win.

Does this suggest that derby participation encourages better performances from worse-playing teams? Unlikely.

This trend is a difficult one to explain solely on derby day performance and does not account for the strength of the schedule leading into games. Naturally, some teams have more difficult schedules leading into derby games, which can explain drops in form. Equally, key players injuries and squad rotation can provide other explanations for playing against form.

Test 2: Do players perform better on average in derby games?

Of course, the breadth of talent level across the URC teams is undeniable, with some of the best players on the planet turning out for their respective teams each week. Consequently, these games often come down to fine margins between teams and the boot of their respective kickers. In tight games, nothing is more critical than converting tries to keep that scoreboard ticking.

For the second test, we wanted to see whether derby game pressure affects kickers and, if so, how does it affect their performance? Do they crack under pressure or are they able to perform? 

To assess this, we used Oval Insight’s comprehensive database to map every conversion attempt in the 2022-23 URC season to see where conversions were attempted and whether they were successful or not.

As you can see, there was no clear difference between derbies and non-derbies.

However, the peripheries caught our eye. Upon further analysis, it became clear that there was something strange about kicks taken from the edges of the pitch (traditionally the hardest conversions to make), so we then plotted the success rate of these kicks specifically. 

What emerged was that kickers were hitting the toughest conversions more frequently in derby games (as taken from a sample of 506 kicks, 121 of which were made in derby games). This exercise also demonstrated the expected drop-off in accuracy for kicks taken from the right-hand side of the field, given the difficulty right-footed kickers face in swinging the ball toward the posts. For example, of the 40 penalty goals attempted from within 15m of the touchline, only 7 were taken from the right-hand side of the field.  

The success rate of kicks from within 10m of the touchline grew 25% in derby games (a 12% increase in accuracy overall), suggesting that kickers are not only able to maintain their composure under pressure, but thrive on it.

However, this theory has limitations, as the later on in the game they attempted the kick, the more likely kickers were to miss (the same was not true for non-derby games). In derbies, the closer the game was to finishing, the less likely a kicker was to convert from within 15m of the touchline – but this was not the case in non-derbies.

Instead, the most likely explanation is that the talent of the kickers on the South African and Irish teams, who alongside the Welsh have 4 teams each in the league, persists despite the pressure of local competition. As they had 8 of the top 10 conversion kickers last season, their continued excellence produces this curious anomaly in the data which helps further prove that the best players maintain their excellent standards under pressure. 

Test 3: Do derby games see more penalties and cards than normal games?

Rugby is an emotive sport and often we see those emotions flare up between teams on the pitch. Tackles coming in a fraction of a second late, or an inch or two too high can ignite tensions and inspire the referee to reach into his pocket.

With the emotive atmosphere that derby games encourage, we wondered if that would impact the number of penalties and cards produced in-game.

In the 151 games played last season, there were 173 cards issued: 15 red and 158 yellow. Of those 173 cards, 49 (5 red, 44 yellow) were issued in derby games (identified as games between teams from the same nation). At first glance, this again would appear to support our theory.

However, again, the numbers do not tell the whole story. Of the 151 games last season, 42 of them were classified as local derbies. Match this trend with the average card issuance per game and we see that the rate of yellow and red cards being issued stays largely consistent between derbies and normal games.

The kicker

If the data doesn’t support it, why do derby games always feel closer, with the final result defined by individual performances and mistakes? Perhaps the answer lies back where we started: the fans and team parity.

When we create the atmosphere and the expectation of a ‘derby’, we imbue the action on the pitch with a deeper meaning. Each tackle feels bigger, each decision more momentous because of the stakes that we place on the game as fans. We feel that these types of games are closer because we hope for them to be – we want to believe that important games are decided by a moment of magic or madness on the pitch; ask any of the Leinster and Munster fans who made the trip to Dublin last weekend!

Ultimately, the parity and quality of competition between the URC squads (and between teams from the same nation) can go a long way to explaining the closeness of local derby games.

We can only hope the incredible clash between Leinster and Munster is a taste of what is to come this season. With Cardiff vs Scarlets and Leinster vs Connacht this weekend, we can’t wait to see another round of incredible action in the URC.

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