"The only way to deliver to the people who are achieving is to not burden them with the people who are not achieving" - Good to Great, Jim Collins
From the same book, same chapter, it says the following:
"The moment you feel the need to tightly manage someone, you've made a hiring mistake. The best people don't need to be managed. Guided, taught, led - yes. But not tightly managed. We've all experienced or observed the following scenario. We have a wrong person on the bus and we know it. Yet we wait, we delay, we try alternatives, we give a 3rd and 4th chance, we hope that the situation will improve, we invest time in trying to properly manage the person, we build little systems to compensate for his shortcomings, and so forth.
But the situation doesn't improve. When we go home, we find our energy diverted by thinking (or talking to our spouses) about the person. Worse, all the time and energy we spend on that one person siphons energy away from developing and working with all the right people. We continue to stumble along until the person leaves on his own (to our great sense of relief) or we finally act (also to our great sense of relief).
Meanwhile, our best people wonder, "What took you so long?"