Per Sam, 33/52 never showed up, left early, had a career ending injury transferred out without playing a significant down at Nebraska, have only been special teams contributors so far or left early, not using their full number of years. Of the remaining 19, seven have finished their careers. Interestingly, the 2013 class had a rivals rank of 17, but I count only 9 of the 25 recruits that year as contributing. Knevel and Marcus Newby remain as 5th year seniors from that class. About half of the 2014 class look to be contributors.
That highly ranked 2013 class did have guys like Collins, Gregory, Bando, and Gerry, but didn't come anywhere near living up to its ranking.