Here is a table of the five year records of some major league pitchers, in fact some of the best in recent history. Many pitched during the four-man rotation era, and many are or will end up in the Hall of Fame. Nobody would say A.J. Burnett is the equal of ANY of them.
Greg Maddux averaged nearly eighteen wins, Curt Schilling sixteen, Roger Clemens fifteen, Nolan Ryan fourteen, and Pedro Martinez ten during this age frame. Sandy Koufax and Don Drysdale were done, and Juan Marichal on the downside.  Here are A.J. Burnett's similarity scores from Baseball Reference. All of these pitchers are pretty good but how many would you want to pony up over sixteen million a year for, for FIVE years? As they say, "a fool and his money are soon parted."