Unfortunately, since Tony Mitchell might not be in the draft, and bigger guys tend to rise when draft day comes, best player available is likely to be Dion Waiters or Tony Wroten.
Both players have excellent upside, and Wroten might be even faster to the basket than Rondo. A 6'5" less intelligent Rondo who could still become an All Star. He could also guard 2s and maybe even smaller 3s, so that when playing with Bradley, Bradley could guard the PG while playing SG on offense.
Waiters looks like a more athletic E'twan Moore, and should be really solid on both ends of the court. An excellent super sub, already accustomed to the role.
The question with Waiters, is the upgrade in athleticism over Moore worth spending a first round pick? Tough call, and hopefully there would be a Harkless, Ross, or Mitchell available to make it easier not to draft Waiters.