The first thing you learn about the trade deadline is that it's the trade deadline. The second thing you learn about the trade deadline is that it's the non-waiver trade deadline, and that moves can and will happen in August. Those moves, granted, are more difficult, so you don't see as many of them. But just last year, August brought a Justin Verlander trade. It also brought deals involving Justin Upton, Mike Leake, Jay Bruce, Neil Walker and Yonder Alonso.
There are deals, therefore, to be made. But this year, there doesn't seem to be a Verlander equivalent. The frenzy leading up to July 31 suggested that teams in the hunt were acting with a high degree of urgency. You don't want to have to rely on August transactions. Teams want to get their business done before that, and we just went through what felt like a deadline for the ages.
So now that it's over: Who added the most value? I assure you there's no perfect way to measure this. But I can give you some numbers.
To identify contenders, I made use of the FanGraphs Playoff Odds page, considering every team with odds north of 5 percent. Then I looked at each contender's player projections, adding up all the projected Wins Above Replacement for players acquired through midseason trades. Below is a table of projected rest-of-season WAR. This does not give extra credit for trades made before the deadline. This also doesn't take into account projected contributions by the players who have been lost or replaced. Finally, although I'd rather look at playoff odds themselves instead of projected WAR, I don't have any way of calculating what the playoff odds might look like had trades not been made. That gets complicated very fast.