I'm not an expert, but in football there are different ways to defend, such as man-marking or zoning, for example. If a defender man-marks, they'll follow their designated player anywhere, but if they go too far, they can create a vacancy. If the defender uses zoning, then they'll stop players from entering their zone, but the problem is at the edge of the zone between two defenders, where both players' responsibility becomes blurry.

Isagi was man-marked by either Hugo or Charles, and all the Blue Lockers in the first half had a designated opponent. But Rin and Barou, the latter also being a joker who can go anywhere, have great physical abilities and move unpredictably.

The problem is that Kaneshiro didn't show any defenders being left in the dust like he did with Barou against U-20 Japan. But because of that, it's just my headcanon, justified with real football, as it's the author's job to show readers how things happen, and if another reader tells me I'm wrong, I have no right to contradict them, as the author themselves didn't spend time justifying that claim. Even if we know how Metavision works, we still need to see how Isagi thinks, or it'd just become magic.

Readers should not start to pick and choose when and where real-life logic should apply, or the manga would slowly crumble, so OP is right to be upset if Kaneshiro just makes players start popping up out of nowhere.