In principle, as a coach/admin, you can easily delete a player from the team. You do this via the menu item "Team" and then land in the submenu "Members".
Then you select the player profile of the corresponding player, edit it using the stylus, navigate all the way down and then select "Delete player".
After that, the player will be removed from the team along with his player profile and thus all his data.
This is different if the player leaves the team. The player himself then no longer sees the team and is no longer part of the team from his side.
However, you as the coach/admin will keep the player's data including player profile and the statistics of the profile.
Since the preservation requires the consent of the player, only he himself can leave the team. As a coach/admin you logically can't just leave your team, someone has to manage the team after all.