The single best tool in handling this situation for me was peer feedback. We instituted a system where peer feedback came from a few peers he selected and a few I myself selected. The person in question was shocked when even the peers he selected came back saying that he simply failed to get stuff done.
This came as a wakeup call for him, and we were able to work on a very clear development plan that minimized distractions and maximized time for deep work. He ended up being a solid contributor.