Hydration Breaks Change the Flow of the Game - A statistical analysis of xG and more
I ran a statistical analysis to see the effect hydration breaks had on match momentum (via cG created). I'll go into more detail below, but summarize the findings right here:
TLDR: Match data suggests that hydration breaks create larger swings in xG advantage before versus after the hydration break in each half, comparing the 2026 world cup with 2018-2022. Total xG and shot activity around the first hydration break also swung more in 2026, and even total attacking activity, regardless of team, swung more across hydration breaks in 2026. Restricting to only group stage games or only knockout or round-of-16 games preserves the pattern, and so the new 48-team format is unlikely to blame for this shift.
Putting aside ad revenue for FIFA and hydration of the players, for teams the hydration break gave a timeout that allows for tactical adjustments / reset. We should expect the momentum and chance distribution to change as a result: Is a team that had lots of chances before the hydration break as likely to continue creating chances after the hydration break as it would have been without the hydration break? Does the hydration break help teams with no chances reorganize to create something? These would lead to swings in chance creation, meaning larger changes in team advantage in xG, shots, or goals. How can we measure such swings in chance creation? The best quantity to look at is the change in a team’s xG advantage from the “first quarter” (Q1), the period of the first half before the hydration break, to the “second quarter” (Q2), the period after it. We then make the same comparison between Q3 and Q4 in the second half. I beg forgiveness for my footballing sin of calling them quarters here.
The above figure compares those xG-advantage changes with the equivalent changes in matches from previous World Cups without hydration breaks. There is a noticeable shift toward larger swings around the break timing in 2026. 2026 saw 20% of matches have an xG swing of 1 or more, which happened in only 11% of world cup matches in 2018-2022. The average absolute swing in xG advantage was 0.47 xG; in 2026 it was 0.56 xG.
Running a statistical analysis that asks, “Are these swings in the 2026 World Cup?” gives a p-value of 0.032. That tells us, roughly, that observing this kind of a signal only as a result of randomness (and not some real underlying effect) is only 3.2%; the hydration breaks seem to have a real, measurable effect. Statistical details, including assumptions, methodologies, and multiple-testing adjustment, are provided at the end of the article.
But hey! Maybe the new format is to blame, since the Round of 32 could just create matches with big chance-creation swings. We can rerun the same analysis on the group stage only (p = 0.050) or the Round of 16 onward only (p = 0.077, with far fewer matches), and the data still points in the same direction; see the figure below. The new format is unlikely to be the reason for these huge xG swings.
Beyond which team holds the xG advantage, there also seems to be a change in overall attacking activity on both sides of the pitch. The plot below compares the absolute difference in total xG and total shots before and after the first hydration break, and the spread for 2026 is quite a bit wider. Average total-xG movement rises from 0.41 xG in 2018 and 2022 to 0.54 xG in 2026 (unadjusted p = 0.063). The corresponding average shot movement rises from 2.49 to 2.90 shots (unadjusted p = 0.053).
for more details, see the substack article here:
Do FIFA Hydration Breaks Change the Flow of the Game? Statistical Evidence of Chance Creation Swings