It may be similar as to why Cain still sees most of the RB snaps despite the fact that he still is clearly not 100% (injury free yes, but hasn't returned to his previous peak during which he was consistently breaking tackles)...but Cain rarely misses blocks and he secures the football, and thus gets a majority of the snaps, even before the other RB injuries occurred. Similarly, one significant reason that came to mind as to why an injured Clifford may still have invoked more coaching staff confidence than the healthy backups is that despite his limitations and subpar play on Saturday, he didn't turn the ball over...if Roberson or Veilleux could make a few plays that Clifford couldn't against Illinois, but yet also were showing a proclivity to turn the ball over in practice, the choice would become extremely difficult and could be questioned either way afterwards since neither choice was ideal...add a couple more positive plays but also a turnover or two and the game result could have been the same or even worse.