The number of lineout steals is the poor cousin in rugby analytics.

But it may prove to be the difference between winning and losing. I think there is a debate to be had over lineout steals.

Judging from the stats that receive constant attention in rugby blogs, newspaper columns and match commentating, lineout steals looks like a rather neglected metric in rugby analytics. It is no surprise either. Matches rarely produce more than two steals, so there isn’t much to say. However, I have come across a study that indicates this little metric might just be the most important. It might predict the outcome of matches and tournaments better than any other.

What the stats say about lineout steals

In 2004, a group of researchers in the UK published a study in the International Journal of Performance Analysis in Sport. They looked at the correlation between 22 key performance indicators and match results. The study looked at 20 matches played by a national premier division team in a particular season. Here’s the surprising finding: of the 22 performance indicators, lineout steals provided the closest correlation with winning or losing. By a huge margin.

Here are the values for the indicators:

Lineout steals and their importance to winning
Lineout steals and their importance to winning

(Note: For some obscure reason the study also measured the correlation between tries scored and the result. It was no surprise to be the best predictor of winning. Nonetheless, I ignore the points indicators in the study due to their obvious correlation with winning and losing.)

Explaining the numbers

I’ll explain the numbers briefly for the sake of clarity. When we say an indicator correlates with the match result, it means that it is higher or lower than the median/average for all matches.

Looking at the top indicator, Lineout success (opposition ball) %, we can see that the team analysed in the study managed to steal roughly 8.1% of the lineouts across all matches. Looking at only those matches that the analysed team won, it stole 14.6% of the lineouts. This is a whopping 79.6% jump up from the rough average across all matches. The statisticians calculated that the Lineout success (opposition ball) % indicator is the only one that’s “statistically significant“.

Statistically significant, meaning that it cannot be explained by chance.

The following graph illustrates just how much lineout steals stands out from the other indicators concerning correlation with match outcome. Including the third most significant correlation. Penalties conceded. Who would ever have thought that?

Now, I know you could argue that lineout steals occur so rarely that the numbers could quickly be inflated by one or two matches where the opposing side is merely inept at securing its lineout. I would counter that the matches in the sample were all played by quality teams and that the vast scale of the deviation most likely negates possible impact from anomalous games (if there were any).

It’s worth noting here, before we move on, that the things we usually assume are decisive for winning and losing, like successful tackles and attacking the rucks, actually seem to have very little relevance to the outcome of matches. Unless, of course, you fail to maintain decent playing standards.

Rugby World Cup stats

Now, let’s get back to the stats about lineouts. I found an interesting stat in the official analysis of the Rugby World Cup 2015. Looking at the sources of possession that led to tries being scored, the lineout is THE top source of possession for scoring tries. By a wide margin.

Here are the stats:

Now, guess which team at the RWC2015 had the highest lineout steal rate in the knock-out phase of the tournament?

New Zealand, the ultimate winner!

It’s complicated

The stats are telling us something, but what exactly, I hesitate to guess at this stage. Part of me still feels that the steals are so rare that we should be careful to attach too much statistical importance to them. I am also a bit worried about using winning and losing as our test of correlation. We all know that the scoreboard often does not reflect the actual performance of the teams.

In tight contests, critical referee decisions, momentary player lapses or brilliance, and luck can and do swing matches one way or the other. The only way to mitigate these types of potential data distortions is to have large samples, which we just do not have.

Still, we cannot ignore the sheer size of the correlation between lineout steals and match outcomes, as well as the considerable gap between lineout steals and all the other indicators.

So, what is it about lineouts that give them this special significance in match outcomes? I have a few hunches, but I think it’s better that the rugby practitioners, rather than the statisticians, answer that question.

Performance indicators study available at here.
RWC2015 statistical analysis available here.

Photos: www.photosport.nz

Author: Willem Van Rensburg

I was raised among Springboks, then matured among Kiwis, and now live among Wallabies. What’s next? I have never been good at playing this game, but what a game! Show me any other team sport that has equal room for the big, small, quick, slow, smart, not so smart. And when they work in unison it is like watching a symphony.

12 COMMENTS

  1. This is why Eddie jones keeps picking Kruis instead of the better performing launchbury and lawes because he gets so many line out steals

  2. It would be interesting to see England’s lineout steal tally compared to its opponents. I just did a quick tally of the lineout steals in the 2017 Rugby Championship. NZ 9, SA 8, Arg 5, Aus 4. This is good news for SA and not good for Australia. If SA keeps on building its lineout attack on the way to the next World Cup, they will be formidable. Conversely, if Australia doesn’t improve its lineout attack on the way to the World Cup, they will find themselves at a serious disadvantage.

    • Howzit Willem,

      Do you think too much time is spent analysing rugby with stats like that instead of concentrating more of those man hours on the park?
      They do have a place in the game but I believe standing in a field with a rugby ball is far more important.

    • Thanks Paul. You are right. We need fine grained data for deeper understanding of the phenomenon. I haven’t come across a source that provides that kind of fine match detail. Please let me know if you come across data that might help.

  3. Great article, really like you’re writing style!

    I wonder, maybe it’s less steals leads to wins but rather losses leads to defeats? Does ‘steals’ include overthrows and other malfunctions?

    Paul makes a great point about throws on the 5m line. If you’re under pressure for the majority of a match and manage to win a penalty which you kick to the corner only for the line out to malfunction, that can have a huge pshycological effect on a team.

    I’ll definitely bare these stats in mind while I’m watching this autumn 🙂

    • I’m glad you liked the article Huw. You are right to wonder if lineout losses isn’t the real culprit that affects performance. I looked at the stats again:
      – The study does not explicitly define what constitutes a ‘steal’, but I think we can safely assume that balls lost to the whistle in the lineout are not ‘steals’, even if the whistle turns possession around. The study has another measure for errors, so I assume that errors in lineouts that invoke the whistle will be counted there.
      – Any malfunction that turns the ball over to the opposition, including overthrows, and is not terminated by the whistle, is therefore a steal (opposition ball).
      – This means we are talking about situations where a team steals the ball at the lineout and can play it immediately to its advantage. It makes sense that such situations would be greatly advantageous for the stealers.
      – Now, if we shift our focus to lineout success (own ball), there is not much difference in success rate between winning and losing situations.
      – This means that there is no clear correlation between LOSING lineouts, which is the same thing as LOWER lineout success (own ball), and losing performances. I suspect the losses to steals are masked by the greater numbers of wins, so that’s why we don’t see the strong reverse correlation for low lineout success (own ball) to losing performances. Make no mistake, LOW lineout success (own ball) IS correlated with losing performances, but not to the extent that you might have expected given the massive correlation between lineout steals and winning performances.
      – The study does find that if you are good at stealing you have a great advantage, BUT, if you are not so good at stealing, your disadvantage is not that significant.
      – This tells me that the act of stealing might have multiple positive flow-on effects for the stealer. It tells me that if you are not good at stealing, you might still have a strong performance.
      – Which makes your comment about the psychological impact of steals very pertinent. I think there is a lot more to investigate here.

  4. Very good stat mate. The transition from attack to defence on first phase can be seen as very important, especially with quick thinking by the opposition. Not to mention the morale lost by the forward pack.

    If you have a quick thinking 10 you can immediately launch an attack against a awkwardly positioned defence or kick for touch as the Back 3 are usually flat in the line. Maybe a sign more teams need to start training this transition even more?

    • Thanks Conor. You are the second person to mention the psychological impact of set piece losses at critical moments in the match. I am very sure the top level teams are coached how to handle that situation. But we are all human, and you cannot always mitigate negative events, particularly not when you are fatigued.
      You make a good point about quickly changing your structure from defense to attack. I have always thought that if you have a defensive kicker standing in the pocket, and the ball is turned over to the opposition, the opposition suddenly has a massive advantage because the kicker for one is not in the defensive line. Quickly spreading the ball across the field from a lineout steal is bound to expose gaps in the defense.

  5. Interesting thanks! And yes, the psychological impact of losing a set piece is significant as every player is focused on the attack, I wonder what a similar analysis would look for “successful intercepts”.
    All the best.

  6. Interesting correlation. Did the research also mention anything about causation? What makes it difficult (for me at least) is that is is not clear which indicators are lagging and which are leading. (i.e. if you are a “good” team you will steal more line outs and you will score more tries … then the line out steals and tries might be very correlated.. but the steal do not cause the try. )

    I do agree that the RWC2015 analysis suggests there is a certain degree of causation. But then again, it’s could be that the underlying cause of both the steal and the score could be something like “quick decision making” .. which also results in taking advantage of the possession after the steal.

    BTW, i do get the research also includes number of tries scored. The research wants to find PI’s as a function of winning and losing. The number of tries scored seems to be an obvious one, but it could statistically be the case that both winning and losing teams score the same number of tries, but the winning teams score more penalties .. in which case the number of tries is not a good indicator of a winning team.

  7. Very astute comment about the distinction between ‘leading’ and ‘lagging’ indicators. I assume, and I think the study does too, that, being the premier competition in the UK, the matches were between capable sides. Looking at all the other indicators, it would seem that the teams were very evenly matched. So I still think there is something special about lineout steals. As you suggest, the lineout metric might be a proxy of another underlying indicator that was not measured. I see your point. We probably need to think about the lineout steal as an exceptionally good attacking platform which gives the stealer inherent advantages to score tries. It would be really interesting to inspect the sequences of play from the lineout steal. I suspect that would give us an idea of what underlying factors drive the success of the stealers.

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