A game of two halves; an analysis of the 2018 league final

Continuing a theme from the previous year, the 2018 national league final proved to be a lopsided affair at Tipperary’s expense. Though not nearly as one sided as Tipperary’s 16 point defeat to Galway in 2017, this was still a heavy loss, and a late goal from a close-range free was the only thing maintaining a respectable final margin for Tipperary.
Unlike 2017, however, this match was still extremely close at half time, Tipperary holding a narrow lead. The last meeting between these two teams saw Kilkenny win by a single point, in a back and forth game, and there was nothing to indicate that Kilkenny would totally pull away in the second half. In this article, we investigate why the two sides were so close in the first half, and what enabled Kilkenny’s big run in the second. 

Some notes on the methodology and terminology
This match was analysed by watching the game, and noting down any time an event occurred. These events include pass attempts, completed passes, turnovers, fouls, shots, wides, points, the sliotar going out of play, and so on. Though total accuracy was the goal, it's possible that there were transcription errors, as well as situations where the action could be interpreted differently.
When passes are described as ‘successful’ below, this doesn’t necessarily mean a clean catch. It simply means that the team who made the pass were the next team to gain control of the ball, even if, for example, the ball was fought over along the way, or the opposing team fouled before the sliotar could be controlled, or the opposing team deflected the sliotar over the sideline. Therefore, the pass success rate is not only a measure of normal fielding, but also of a team’s ability to emerge with the sliotar from a drawn out scrum.
The turnover categories are labeled as ‘interceptions’, ‘steals’, ‘sideline’ and ‘fouls’. As implied, sideline turnovers are when the team in possession send the sliotar over the sideline, and foul are when the team in possession loses it due to committing a foul. Interceptions are when the opposing team gain possession from a failed pass, while steals don’t require a pass; this is when the opposing team gain possession after causing the player in possession to lose control of the sliotar. All possessions either end with a shot, or a turnover. If a shot is deflected, either by an opposing player or by the goalposts, it is considered to be a new possession once the sliotar is controlled again, even if they player now in possession is on the same team that shot the ball.
Points per shot, as the name implies, is how many points were scored per shot taken. Since this includes points from goals, the maximum theoretical value is 3, which would occur if every shot resulted in a goal, while the minimum would be 0, if every shot missed. For some reference, the previous articles involving shot charts or a match analysis (covering 8 different matches) found a median points per shot value of 0.65 and a mean of 0.653, though keep in mind that this is a small sample size, and, because these matches were all knockout-stage games or finals, often featured stronger teams.

Shot charts
Starting off, let’s get into the most important factor of all: the scoring. How was each team getting their scores? Where were they taking their shots? How was their accuracy?
Below are shot charts for Kilkenny and Tipperary, both for the entire match and divided by half. A white dot indicates a point, green indicates a goal, black indicates a wide and red indicates that the shot was saved. A blue border is a shot from a free, a magenta border is a shot from a sideline cut and a cyan border is a shot from a sixty-five.
 

Here we see our first tangible divide between halves; in the first half, both teams were shooting extremely similarly. Tipperary took only one more shot than Kilkenny, and both teams had the same number of wides, though Kilkenny had also saved a Tipperary shot. Kilkenny scored an extra point, but Tipperary scored an extra goal. Both teams scored 5 points from frees, and one from sideline cuts. Both teams were shooting from similar locations, though Kilkenny were forced into shooting from distance more often than Tipperary. Tipperary were scoring 0.765 points per shot to Kilkenny’s 0.688; both good values in terms of efficiency.
The second half was a totally different story. Kilkenny took half a dozen more shots than Tipperary. Kilkenny managed two goals and five points from play, while Tipperary only scored a single point from play, relying almost entirely on frees to keep them in the game. Though both teams had 9 frees in the half, Tipperary were in a position to shoot from only five of them, compared to Kilkenny’s eight. Tipperary’s scoring efficiency rose to a very high 0.833, but Kilkenny’s rose to an unbelievable 1 point per shot. In other words: If an opposing team had taken the same number of shots as Kilkenny, they would have to point every shot to merely draw. For Tipperary to win this half, they would have had to have scored more goals, or forced more turnovers, neither of which they succeeded in. Looking at the shot locations for both teams, there was a clear breach in Tipperary’s left and centre backs. Again and again, Kilkenny were able to get shots at extremely close range, coming through the centre or right-hand side. This includes four shots (resulting in two goals and a point) from within the 20m line, compared to two shots from Tipperary, both of which were saved. More so than shot location, the deciding factor just appears to be volume; why were Kilkenny able to shoot so much more than Tipperary, especially from play? It’s time to look at turnovers...

Turnovers
The chart below shows how many times each team had turned the ball over as the game progressed:
 

Once again, the numbers were very close for the entirety of the first half, with neither team pulling very far ahead of the other, and the lead going back and forth. However, as the second half wore on, Tipperary’s mistakes piled on. The chart below displays the difference between scores and the difference between turnovers at the end of each minute of play:
 

The consequences of Tipperary’s turnovers are extremely clear here: there is almost a mirror image between the scores and the turnovers! With both teams shooting so well, with very few wides on either side, it was Kilkenny’s extra possessions which allowed them to really gain ground.
In terms of how the turnovers were created, the sources were similar for both teams;
 

In each case, the vast majority of turnovers came from intercepted passes. Kilkenny allowed a few more balls go over the sidelines, and Tipperary lost a few more possessions from steals, but overall the proportions were similar. However, Tipperary still had 11 more turnovers from interceptions. Even if they had avoided turnovers by any other means, their best outcome would still have been roughly the same number of total turnovers as Kilkenny. This leads us to look into the passing in more detail, to see the breakdown of where all these interceptions happened.

Passing
The following chart breaks down the different types of pass each team made, and how many of these passes were successful. The categories are handpasses, short passes from play, long passes from play, short puckouts, long puckouts, passes from frees, passes from sideline cuts and passes from sixty-fives.
 

Proportionally, there’s not a huge difference between the teams. Tipperary made more long puckouts, and more passes from sideline cuts and frees, but also made fewer long passes from play. Overall, Tipperary did make significantly more passes, but were completed their passes at a worse rate than Kilkenny. In other words, it seems likely that Tipperary may have been victims of over-passing, and struggled against Kilkenny’s better fielding.
 

The chart above shows the raw numbers for how many failed attempts each team made at each type of pass. Here we can see that both teams struggled with their long passes; in total, neither team had better than coin-flip odds when making long passes, with Tipperary succeeded 50% of the time, and Kilkenny slightly below that. However, Kilkenny were slightly better in almost every other area, and were massively better in long puckouts. In the first half, both teams were able to keep possession from half of their own long puckouts. However, in the second half, Tipperary took an extremely sharp dip, only succeeding in retrieving 1 in 6 of their own puckouts! Kilkenny weren’t terrific either, only completing about 29% of their long puckouts, but they compensated by switching to shorter puckouts, leading to a total second half puckout success rate of 44%.
This dip in puck-out success could really be a large part of the root of Tipperary’s struggles in the second half. Kilkenny had the far more experienced keeper coming into this game, and it paid dividends. While Eoin Murphy had some more spectacular highlights, saving multiple Tipperary attempts on goal, it was his more consistent puckouts which really enabled Kilkenny to stretch their lead. 
In a game where both teams were shooting with tremendous accuracy, and where both teams it very hard for the other to hold on to possession, Kilkenny were able to fight that little bit harder, shoot that little bit better, and pass that little bit more accurately. In the end, these factors all stacked up, and Tipperary faded.