See Topgrading[1]: "Simply put, topgrading is the practice of packing the team with A players and clearing out the C players," Smart writes. "'A players' is defined as the top 10 percent of talent available at all salary levels--best of class. With this radical definition, you are not a topgrader until your team consists of all A players. Period."
[1] http://www.amazon.com/Topgrading-Leading-Companies-Coaching-...