Kicking in Elite Rugby Union
Why there is so much kicking in elite rugby union – and how to change it
Rugby union finds itself at a fascinating crossroads. On one hand, the sport has just celebrated a remarkable men’s World Cup, with the quarter-final weekend in particular heralded as one of the most enthralling in living memory. Seven of the eight knockout fixtures were within one score in the final five minutes. There were some outstanding performances from Tier 2 nations, including Fiji, Portugal and Uruguay. And the total global TV audience for the tournament was over 800 million.
On the other hand, there has been a lot of public commentary about how rugby union looks at the elite level, and whether the laws should be tweaked to improve the game as a spectacle. One area that has sparked heated debate is the amount of kicking: why it happens, whether it is a bad thing, and if so, how to change it.
To answer some of these questions, the data science team at Oval has decided to dive into the numbers, using Oval Insight, our new analytics platform. The platform has been built in collaboration with TruMedia, and harnesses the same graph database structure and query software used by teams in the NFL and MLB.
How do teams progress the ball in other sports?
Before we get stuck into rugby union, it is worth zooming out and looking at other ball-based “invasion sports”, for a bit of context. These include football, American football, Australian rules football, basketball and both types of hockey, among many others.
In all of these sports, there are several ways to progress the ball up the field. Broadly speaking, you can move forwards by (a) running with the ball, (b) throwing it, (c) kicking it or (d) hitting it.
Interestingly, from what we can calculate using publicly available statistics, rugby league is the only sport in which running with the ball is the dominant mode of ball progression. Oval’s data from the NRL shows that teams typically make just over 70% of their metres from carrying the ball (defined as metres over the gainline or from the point of first receipt) as compared to kicking it (defined as metres from the starting location of any kick in open play).
In all the other sports, the main mode of gaining territory is throwing, kicking or hitting the ball forwards. In the NFL, for example, only 36% of yards in the 2022-23 season came from rushing (carries without any proceeding forwards pass).
Anecdotally, some sports started out in the 19th century as mainly running games. The earliest forms of association football, for example, had a heavy emphasis on dribbling. But over time, the dominant teams in almost every sport have found that carrying the ball is a less effective way of bypassing defenders than throwing, kicking or hitting it.
Rugby union makes it harder to carry the ball than others sports do
Compared with other sports, rugby union has three features which make it harder to run with the ball.
- The number of defenders: with 15 players on each side, rugby union has more defenders than almost any other sport, except for Australian rules football, which has 18. However, teams in the AFL play on ovals that are roughly 3 times as big as a standard rugby pitch.
- The formation of defenders: in almost every other sport, the offside laws permit attackers to go ahead of the player in possession, which scatters the defence around the field. The two codes of rugby are unique in prohibiting this. However, rugby league forces the defence to retreat 10m after every tackle, which automatically creates space for the attackers. Rugby union is the only sport in which as many as 14 defenders occupy a single line, which does not have to retreat.
- The penalisation of attack: all of these sports allow turnovers in open play, but rugby union has by far the harshest punishments for losing the ball. A handling error can lead to a scrum, which is a dangerous platform for the opposition. An error at the ruck frequently leads to a penalty in favour of the defence. At the 2023 Rugby World Cup, the attack was actually penalised more often at the ruck than the defence was (219 v 213).
Though most sports have some sort of limitations to make it harder to run with the ball – NBA and AFL players have to bounce it, for example – the obstacles to carrying in rugby union are especially severe.
Defence in rugby union has improved over time
Analysis from other sports has shown that increasing professionalisation can lead to greater improvements in defence than in attack. In football, for example, the number of goals scored per game declined from about 4.5 in 1890 to 2.6 in 1990, according to Chris Anderson and David Sally, authors of “The Numbers Game”.
In rugby union, the picture is nuanced. Users of Oval Insight can access the remarkable historical database of Stuart Farmer Media Services, going back to the first test match in 1871. When looking at men’s matches between the current Tier 1 nations (see below), the data actually shows that there has been a long-term increase in tries, with a higher rate so far in the 2020s than in any previous decade. (Part of the increase in the last decade can be explained by teams taking fewer shots at goal.)
However, it is also true that defences have improved substantially since rugby union turned professional in 1995. A key indicator of this is the rate of missed tackles. At the 1987 World Cup, defenders missed 30% of tackles. At the 2023 World Cup, this figure was 13%. In other words, the rate of missed tackles today is less than half what it was in the amateur era.
How can it be possible that teams are scoring more tries, yet defences have also improved substantially? One explanation is that games last longer, with ball-in-play rising between 20-30% since the amateur era, creating time for more scores.
Another factor is that the modern teams use a wide array of tactics to reach the try line, including dominance of the set-piece, extracting penalties at the breakdown, and earning territory through kicking. In fact, in the last two years, more than half of tries scored in men’s Tier 1 test matches have come from possessions that start in the attacking 22, rather than carrying the ball from further back. (Of those tries, almost 90% come from lineouts, scrums or tap penalties that occur in the attacking 22.)
The dominance of defence (and kicking) is higher at the most elite level
So far, we have learned the following:
- In most sports, passing or kicking the ball forward is easier than carrying it.
- Rugby union has several unique obstacles that make it especially hard to carry the ball forwards.
- The quality of defence has improved substantially in the professional era, with the rate of missed tackles falling by more than half.
But another key feature of modern rugby union is that the higher you go up the professional pyramid, the better the quality of defence is relative to the quality of attack.
Using Oval’s men’s performance data from matches in 2023, we have divided the professional game into three divisions: Tier 1 Test, Elite Domestic and Domestic (full definitions in the table below).
The clear takeaway from the data is that the pinnacle of rugby union is dominated by defence. Relative to professional sides lower down the pyramid, Tier 1 international defences miss fewer tackles, win a higher fraction of penalties at the ruck and concede fewer tries.
This dramatically changes the shape of the game at the highest level, and therefore the tactical approaches that are most successful. In 2023, Tier 1 teams that had more kick metres than their opposition won 79% of matches, whereas sides that had more run metres won only 59% of matches. The importance of defence in the international arena is further underlined by the fact that the team that won more turnovers was victorious in 74% of matches.
In domestic professional competitions, these metrics are all in greater equilibrium – and in second tier leagues, carry metres start to overtake kick metres as the best predictor of who will win a match. Given the direction of this trend, it seems likely that grassroots rugby will be tilted further towards the running game and away from kicking and defence.
Overall, the data present a clear picture for why kicking is so common in the modern elite game. At the very highest level, where defences have the upper hand and turnovers are so pivotal, putting boot to ball tends to be the most effective strategy of gaining territory (which is essential for scoring tries).
What law changes would reduce the importance of kicking?
With all that being said, kicking at the international level may not be as rife as people think. There is actually less of it in the professional era than there was in the amateur era, despite there being more ball-in-play time. At the 2023 World Cup, there were roughly 30% fewer kicks per minute than in the 1987 edition.
Another illustration of this is that the 1973 match between the Barbarians and New Zealand – widely considered to be one of the greatest of all time – had 106 kicks in open play. The highest total for a match at the 2023 World Cup was 82. Combined with the fact that international teams are scoring more tries than ever, this suggests that the game might be in better shape than is sometimes assumed.
Nonetheless, if fans, pundits and administrators do want to reduce the importance of kicking in international rugby union, the data above implies that the most important area to address is probably making things tougher for defences. Many of the law changes that have been proposed aim to make it harder to kick: for example, enforcing the 5-second rule, banning the caterpillar ruck or tweaking the 50/22 law. However, the real problem seems to be that it is too hard to attack: international defences are too good at tackling and winning penalties at the breakdown. These factors seem to be driving the higher prevalence of kicking in Tier 1 tests.
Of course, law changes are easier in theory than in practice – they don’t always have the effect that officials want, and can have large unintended consequences. But there is one variation for which there is a lot of empirical evidence that it will tilt the balance from kicking towards carrying: having fewer players on the field.
The importance of creating space
As we noted at the start of this article, the challenge for rugby union (relative to other sports) is a lack of space between defenders: it is unique in having a solid line of up to 14 players.
One solution to this would be to increase the size of pitches – which unfortunately would be impossible in many stadiums. But what happens when we do the alternative, and take players off the field?
There is ample evidence from the world of rugby 7s that having fewer players on the field reduces the rate of kicking and increases the rate of try scoring. In the 2020 World Rugby HSBC Sevens Men’s Series (full technical report here), there was only about one kick for every ten possessions, which represents an 82% drop from the 15-a-side game.
Similarly, there are roughly three tries for every ten possessions, which is a 350% increase from 15-a-side matches. 7-a-side rugby is played under very similar rules (with some variations), but the amount of space makes it much easier to carry the ball, and therefore less attractive to kick it.
Fascinatingly, the prevalence of yellow and red cards in elite 15-a-side rugby means that we now also have a hefty sample of men’s games in which both teams are down to 14. Using the Oval Insight query tool, we are able to isolate possessions in which the attack and defence are both a man short. The results are striking: compared with 15 v 15 rugby, 14 v 14 has 6% fewer kicks per possession and 28% more tries. There is also a sharp increase in the fraction of unsuccessful tackles, from 20.50% to 22.44%, which is likely a result of the defence being more stretched.
When plotted on a scatter chart, all of these findings are consistent. They also provide an equation for how subtracting players from the field would likely affect the rate of kicking and try-scoring.
Of course, there are other law innovations that could have the same impact – creating more space for the attack and more stress for the defence – with less upheaval. For example, officials could penalise the attack less often at the breakdown, or move the offside line backwards at the ruck (to where it is for scrums and lineouts).
Alternatively, restrictions on the number of players could be introduced as temporary “powerplays” during matches. This could be similar to how the T20 and ODI cricket formats limit the number of fielders on the boundary at the start of an innings, to incentivise more attacking play.
Whatever the innovation, the answer from the data is pretty clear: rugby union has more tries and fewer kicks than it used to. But if fans want to see those trends go even further, the laws need to create more opportunities for the attack to carry the ball, and fewer obstacles that benefit the defence.