I am quite sure that you know how to use Google. There are plenty of mock drafts that have Kelly going in the late second round. There is a conversation with Chad Ford that had Kelly going mid-second round prior to his injury.
Asserting that Kelly is not good, which is what you explicitly stated, suggests you are either ignorant when it comes to basketball or that you are just so far up Roy William's ass that you cannot see anything from Duke as good.
Will Kelly do well in the NBA? I do not think so. He will probably be a journeyman. But, he will be on an NBA roster at some point in the future. I would say that is pretty good and that it puts him above most college basketball players.
Further, I would say that any college basketball team that loses a potential NBA pick midway through the season is going to be greatly impacted. When good teams only run about seven deep these days, losing any starter hurts; losing a starter that will play at the next level is almost irreplaceable.
If KU lost Whithey, McLemore, or Johnson at this point, I would expect them to limp to the finish line. They could still come out and beat some good teams, but they would not be able to survive any type of an off-night. The same thing is happening with Duke. If Duke is on, this Duke team can still play with anyone in the country; but, the moment that contested shots on not falling, this Duke team is average at best, because they have lost someone whose presence on the court created uncontested opportunities for everyone else.
UNC lost Marshall last year and they were blown out by a KU team that, talent-wise, had no business being on the floor with UNC. Am I going to say that UNC was not a great team with Marshall? No. That is absurd. Marshall was able to create opportunities for everyone else on the floor. When he was out, UNC was forced to take more contested shots.