Jim Mora announced on Monday, after UCLA's first practice of the fall, that Clark has mono, which is a relatively minor illness for some, but could present more significant issues for an athlete since it can cause fatigue and affect endurance.
Clark, when he does eventually see the field, projects as a complete tight end, with the ability to block, catch, and split out wide when necessary. As it stands, UCLA's offense doesn't use a tight end all that much, but the Bruins were projecting to incorporate more tight end formations in the offense to include Clark.
Now, it looks like those plans could be put on hold until Clark gets healthy. Colby Cyburt, a former offensive lineman, could see more time in Clark's stead, and Nate Iese, currently a fullback/H-back, could also practice more as a tight end if UCLA is dead-set on using the tight end in the offense this year.