Substitute during live ball

[jra104]

Fed rules tournament. 15u. Batter draws a walk, runner at 3rd. While going to 1st, team in 3rd base dugout swaps 3rd baseman with bench player. Having 10 in filed at one brief point.
What’s the consequence of this?

[ilyazhito]

This is an illegal substitution. The extra player is removed from the game.