At first glance, the format of the World Men’s U16 Championships sounds surprisingly familiar.

There are 36 teams, no traditional groups and one large table. Each nation plays four different opponents, with the top eight progressing to the quarterfinals.

It sounds a little like football’s new Champions League league phase. There are also 36 teams in that competition, with each club facing only eight of the other 35 before everyone is placed in one table.

However, the similarities end there.

In the Champions League, the table still works as most supporters would expect. A win earns three points, a draw earns one, and teams level on points are initially separated by goal difference and goals scored. The strength of their opponents can eventually be used as a later tiebreaker, but it does not change the number of points earned from each match.

At the U16 World Championships, there are no conventional points. Instead, every performance is converted into a rating using the Tournament Performance Index, or TPI.

That is why an unbeaten team can sit outside the top eight, while a team with a defeat can be above them.

What exactly is the TPI?

TPI explained in 20 seconds

Every team receives a rating for each match.

Result and winning margin:

Win by six or more: 75 points
Win by three to five: 70 points
Win by one or two: 65 points
Win on penalties: 62 points
Lose on penalties: 38 points
Lose by one or two: 35 points
Lose by three to five: 30 points
Lose by six or more: 25 points

A second number is then added depending on the opponent’s pre-tournament ranking. Playing a highly ranked team is worth considerably more than playing one near the bottom.

The ratings from all four matches are then averaged to create the team’s TPI.

World Aquatics designed the system to compare teams that have not faced the same opponents. It rewards dominant victories, close defeats against strong teams and wins over highly ranked opposition.

On paper, there is logic behind it.

With 36 teams and only four preliminary matches, simply awarding two or three points for a victory could heavily favour teams handed easier schedules. The TPI attempts to recognise that beating a leading nation is more impressive than defeating one of the tournament’s weakest teams.

It also encourages teams to continue playing for goals. Once a team wins by six, it receives the maximum result score, meaning there is no additional TPI reward for winning by 15 or 20.

The problem is that the system depends heavily on the accuracy of the rankings used before the tournament.

Russia are the clearest example. They had not competed internationally during the previous four years and therefore entered the competition without a ranking. Under the system, an unranked team is placed near the bottom of the pre-tournament order.

Russia are clearly much stronger than that position suggests.

As a result, Russia can collect a huge rating by defeating a highly ranked opponent. Their opponents, meanwhile, receive very little credit for facing Russia because the formula considers them a low-ranked team.

Russia’s penalty-shootout victory over Montenegro earned them 99.2 TPI points. Montenegro received only 38 from the same match, despite losing narrowly to one of the strongest teams in Zagreb.

This is where a system intended to correct unfair schedules can instead create another form of unfairness.

Greece provide another striking example. They defeated Spain 9-8 and Puerto Rico 23-3 but were only 19th after three matches. Even a victory over Hungary by six or more goals — the largest winning margin rewarded by the formula — might not be enough to reach the quarterfinals without help from results elsewhere.

That does not automatically mean the TPI is a bad idea.

One view from Zagreb is that teams know the possible rewards before each match. Their job is therefore simple: perform as well as possible, reach the maximum six-goal margin and avoid worrying about other results. Supporters and coaches may also become more comfortable with the system once they have seen it used several times.

The biggest concern may not be the calculation itself, but the draw and the rankings feeding into it.

Water polo has enormous differences in quality across 36 countries. The gap between the first and eighth-ranked teams may be relatively small, while the difference between eighth and 18th can be huge. Broad seeding pots cannot guarantee that every team receives a genuinely comparable schedule.

Returning or unranked teams also need a realistic provisional position. Treating a team such as Russia as one of the weakest nations in the competition distorts the ratings of everyone who faces them.

The Champions League has shown that one large table can work even when teams play different opponents. Its advantage is that supporters can still understand the basic calculation immediately: win matches, collect points and improve your goal difference.

The TPI asks supporters to consider the result, margin of victory, opponent’s ranking and the ratings collected across four different matches. It may be mathematically defensible, but it is not easy to follow.

More seeding pots, provisional rankings for returning teams and a live official TPI calculator would all improve the format.

A tournament system does not only need to be fair. It must also allow players, coaches and supporters to understand what is happening.

Right now, the biggest talking point in Zagreb is not always who is winning. It is whether anyone knows what those victories are actually worth.

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