This is simply not the case. If teams are in a position to contend come mid-July they are more willing to overpay via trade for a postseason run. Because of this, there is generally a hotter market for the rental player amongest contending teams. Also, in Bumgarner's specific case, he's coming back from a injury/decline, so if he has a monster, bounce back to form first half, his trade value will skyrocket from where it's currently at. A monster bounce back first half is the only way he might get a similar return at the deadline to what he probably can get now. A reminder any trade now, the team can make a QO to MB. Traded at the deadline eliminates the QO, so there would be no comp pick. You need a perfect storm to happen to get a Cubs style overpay at the deadline, it's much smarter for the Giants to trade now than hope for the perfect storm in July.