SAR 1 is right, you can't throw Mark out with the bathwater until you see what he can do with players around him & legitimate threat at running back.
You put McCoy behind Mark & see if DBs & safeties are crawling all over his azz at the snap of the ball.
Greene makes it to easy for the defense to cheat, because he's not a threat to get to the next level so it squeezes the field that much more. No one here is saying Sanchez is great, no one, but we have seen him have really good games.
Remember that the Chargers once traded Drew Brees. Brees obviously is a more accurate QB but he still "GOT BETTER" later in his career.