Williams played 21 minutes vs Indiana on Saturday 2/11 - (EDIT - that was over a week ago, he missed their last two games) and between 28-32 in the three games before that. He's been a key part of their rotation.
Jett Howard is their 2nd leading scorer behind Dickinson. He is probably their 2nd most important player on the season.
Barnes isn't much of a factor.
Looking at this another way, they have five players that have started 14+ of their 16 conference games. Two of those players are Howard (29.9 minutes) and Williams (26.3). Their other starters are Dickinson (Cliff, stay out of foul trouble and make him work); Bufkin (6' 4" guard, very talented on O), and Dug McDaniel (listed as 5' 11", we've got to use our size advantage with whoever he is trying to check).
This would be a massive equalizer if both are out tonight.