The Rays traded for White Sox reliever Jesse Crain. But Crain is on the DL and it's not clear when he'll be back. In a brilliant arrangement, the player the Rays send back to Chicago will depend on just how healthy Crain is.

"The return will be based on how much he pitches the rest of the season," the Chicago Tribune reports. Presumably the Rays gave the White Sox two or more "tiers" of prospects, and which one they'll choose from depends on how many appearances Crain makes. It's complicated enough that MLB had to go over it a second time to make sure.

Crain, an All-Star this season, hasn't pitched in more than a month with a shoulder strain. He suffered a setback last week, and it's not known when he'll be ready for action. The Rays believe he'll be back—but back in early August and back in mid-September are two very different animals to a team currently a half-game out of first place.

So what we have is an entirely fair trade of a sort I don't think I've ever seen before. (Though it's rare that a player on the disabled list is traded at all—the last I can think of is the White Sox acquiring Jake Peavy in 2009.) When trading away an unknown quantity, why not wait to see just what you're giving up before getting your return? Well done, Player To Be Named Later; you're everything the scouts said you'd be.