McNeeley was considered a surefire lottery pick and even was invited to the draft, yet he ended up going 29th. He lacked consistency shooting the ball (38%), especially from 3 (32%) and I think it scared a lot of teams off from taking him in the lottery because they figured he wasn't ready to contribute yet.
Mullins shooting struggles haven't been as bad (42% and 33.5%), but the story is somewhat similar. Both guys were expected to be much more consistent 3 pt shooters and more efficient offensively as freshmen. Because of this, I can see Mullins also getting picked outside the lottery. Maybe not as big of a fall as McNeeley, but somewhere in that 16-25 range.
Either way, I would expect him to spend his 1st season primarily in the G League and it all depends on if he wants to do that to continue his development, or come back to UConn, make some good money, and compete for another Final Four.