The final third of John Mozeliak's tenure as president of baseball operations for the St. Louis Cardinals is characterized by a variety of flaws. Foremost among those downfalls was an unwillingness to trade a player at his peak value.
This is a fine line for general managers and POBOs to walk; if a player's trade value is at an all-time high, there's a good chance he's providing plus value to your team. You don't want to get rid of a player who is a valuable contributor for your team. The flip side of this argument is that a player at peak trade value will only lose said value as he ages and gets closer to free agency and the dreaded age-30 bracket.