Something that has been a trademark of Rugby Challenge since the very first one is the way players break or stand in tackles.
What generally happens if your player is strong enough and breaks the first up tackle, is that immediately following that moment, nearly all forward momentum is lost and he'll stand in the tackle, going nowhere for long enough that another player will try and tackle him from another angle, bumping him away in that direction, sometimes followed by another and another, before your player is brought down, usually not far from where the first tackle happened.
When all viewed as one play, it looks like your player is tipping and rocking around on the deck of a boat for a few seconds.
I don't know how hard it would be to program as a change, but perhaps if the player kept the momentum of the direction the player is holding, but lost some speed/stamina from each tackle until brought down. During the first tackle, if it's broken, very little speed should be lost to prevent a convergence on him, which begins a chain reaction of tackles. If you look at an International player hit the line and break one tackle, they might drop from 9