[krajzeg]

While impressive, volleyball is one of the most formulaic sports when it comes to predicting what happens next. This is not a dig on volleyball (I'm a fan!), but it is how the sport works.

The first touch is always about receiving the ball and passing it cleanly to the setter. The second touch is about setting up the attacker (if possible). The third touch is a spike or other attempt to get the ball to the other side. The only significant decision points are usually who the setter chooses for the attack (among 2-4 players depending on formation), and on the defense side, where the blockers jump (3 players choosing spots to cover). Since the algorithm only predicts "actions", both of those don't matter (the setter is going to be "setting" regardless of who they choose, the blockers are always going to be "blocking" regardless of the spot they cover).

The "team strategy" part is in effect just a check of whether the algorithm knows what is happening on the court at all. Volleyball allows the aforementioned three touches, and what the team is doing for each touch is pretty much immutable (the only source of variation is if one of the "steps" fails).

This is of course still an achievement, but the choice of sport gives the researchers a leg up, since volleyball has significantly fewer "degrees of freedom" than other sports. In that context, ~80% accuracy at predicting an action 2 seconds out is less interesting, and it's unlikely that it's anywhere close to human performance for this particular sport.

[vander_elst]

Thinking the same thing! Volleyball is very structured, there are schemas and tactics basically for every event in the game. Additionally, at professional level the accuracy of the players is quite high so the variability should get lower e.g. the setter will set the ball very precisely and the spiker will attack from a specific position. What it might change is the timing (depending on how high the ball is), but usually the professional games are very fast so that should also simplify things.

[fatnoah]

> This is not a dig on volleyball

I see what you did there!