My perception is the commentator thinks the player is secured/consciencent of what he is doing in the match. So, I think it is an idiom. Or the player is really trying an unusual trick standing on the ball...

In the context of the recording it is an idiom, it means he handles the ball well. A different idomatic meaning for "On the ball" when not used in a sports context is that the person pays attention or is prepared. Example Bill is always on the ball with his reports. They always get turned in before the deadline.

In football it's a literal idiom, "he's so composed when he's in possession of the ball". But the phrase is used elsewhere metaphorically to mean "alert". Example: "Don't try to trick that student, he's really on the ball."

It's usually an idiom, but here I think it's literal.