Elidibus hadn't intended to participate in the game. Or the lessons for that matter, but he was still lingering around since Emet-Selch had been convinced to do so. Loosely on the sidelines, he might very well have been looking like a person who deserved to have a ball kicked at their head because they refused to participate in something fun like sports.

So clearly it's okay that Eda does so and at least she calls a warning.

Elidibus also knows the sport is not something you're supposed to use your hands for. Unless you're the goalkeeper? Or was that the local 'soccer' variation? He reacts quickly, in part because he's observant and also because of Eda's call, resulting in catching the fast-traveling ball with gloved hands.

There's clearly a moment where he considers simply throwing it back and bowing out. Instead Elidibus approaches Eda.

"Were you in need of a practice partner? I do not intend to participate, though I would not mind aiding you for a time."