Queue "stand ready" animation. Do note that some units do not have that specific animation, but still they will play their "stand" animation normally - The downside is that, for example, a footman might play an anim that doesn't fit being in a fight.
*footman attacks... then drinks from his bottle*
Another solution would be editing your model animation name with Mago's Model Editor, changing it from "attack slam" to "attack alternate" - that name is just an example. Then critical strike won't be able to play that anim anymore.