Over at Pro Football Focus, Donald recently came in at #18 overall for his 2014 rookie season:
What a rookie year! Donald didn’t start until Week 6 but still managed to not only log 724 snaps but also earn the highest grade of any defensive tackle. That was the level of dominance the former Pittsburgh Panther produced. There was a feeling he was too small heading out of college but his ability to penetrate made him more than just a situational player, with him earning marks in run defense comparable to his excellent work pass rushing.
Best Performance: Week 10, SL @ ARZ, +5.7
It's a pretty big disparity, though PFF is pretty adamant on these rankings being for 2014 alone. I expect the NFL 100 isn't quite as selective in ignoring previous accomplishments. It's something I'll refer to again if Robert Quinn makes the NFL top 60 while coming in at 92 on the PFF top 101.
In the end, it's a sign of the direction of the team to have two defensive players listed by both their peers and analysts.