He might be the bigget "head case" in the NFL. He skipped last season and was diagnosed with post concussion syndrome. He's been cleared to play by his doctors. He almost retired a year ago. One more concussion may just force him into that decision again. That being said, he's a very good young player when healthy, and he's under contract for 3 more years. For the equivalent of a 4th round comp pick, he's well worth the risk.
Denver's defense was dead last in the NFL last season in covering TE's and RB's. Elway just addressed the Achilles heel of this defense. The odds of doing that with a late 4th rounder in this draft were slim to none. Great trade IMO.