The Physics and Tracking Tech Behind the Croatia–Portugal Offside Call
The Croatia goal getting ruled out against Portugal feels like one of those VAR moments where the entire debate turns on a piece of evidence most people can’t actually evaluate.
I went down a bit of a rabbit hole on this one and looked at how the connected-ball system actually works (it’s an IMU inside the ball picking up acceleration spikes and then inferring contact from that signal). The key issue isn’t whether the tech exists, it’s how confident you can be that a tiny spike actually corresponds to a meaningful touch rather than noise or modeling choices.
What makes this tricky is that at the scale they’re talking about (basically a graze, with hair if you take Matanović’s account), physics impact on the ball is so small it’s basically impossible to confirm visually, and even hard to contextualize without the raw signal. So you end up relying entirely on FIFA’s processed output.
FIFA’s own guidance on this kind of situation also matters here. They’ve previously said that hair is only considered part of the body for offside if it affects the movement or trajectory of the ball (typically more than just incidental contact). So the bar isn’t just “did something actually register”, it’s whether it meaningfully changes the play.
And that’s the part that bothers me, the broadcast graphic is basically a single unlabeled spike shown as “proof”. The question isn’t just “do you believe your eyes” anymore, it’s what the sensor is measuring, how precisely it can detect and timestamp a contact, and how much uncertainty gets hidden when that signal is turned into a binary decision that can erase a goal.
I wrote up a longer breakdown if anyone’s interested., it’ll be interesting to see the impact of this kind of opaque, imperfect tech n the game going forward.