Cleveland traded Bob Wickman to Atlanta for a Class A catcher. While Wickman has struggled at times, he still has closed in the past. He's definitely a better option than Williamson and you could argue Howry based on salary and the history of closing. Wickman might be a similar choice to Dempster except for the contract (Thanks Hendry). It does show the current market price for relievers. Not very high.
The prospect, Maximiliano Ramirez, is hitting .285 with 9 homeruns. He is a prospect but not on Atlanta's top 10 per BA.