As a junior, he's got a decent chance at getting full slot money. As a senior - and limited to a reliever role -, he'd basically have to sign for whatever was offered, which would be considerably under slot. And by "considerably", I mean hundreds of thousands of dollars.
I wish he was around for the Pirates 4th round. They could use him in the pen right now. While the Yankees injury situation got all the press, the Pirates situation has been much more devastating, especially in the rotation and bullpen.