I believe there is an extra round after for the extra player (D, F or G) that can replace your lowest scorer of that category.
Yep there is a final round where we can pick a foward or a defenseman, but no goalie, that extra player is like a joker in your hands since he can be swapped at the end of the tournament for your less productive player of the same position.
Not sure if Im clear, but if you pick a foward as extra, he can be swapped for another foward only. If you pick a defenseman as extra, you can swap him with a defenseman only.