The Average Draft order shows a general picture of how your draft will unfold and where values/sleepers and bad values/busts likely exist. Any green highlight means the player is a good value that could be taken earlier. A red highlight signifies an overvalued player that is a bad value or just too high of a risk for that spot. No color means the pick is a reasonable value at that spot.
See also:
Sleepers and Value Picks: Quarterbacks
Sleepers and Value Picks: Running Backs
Sleepers and Value Picks: Tight Ends
