I’m not sure the Diamondbacks need a closer because it’s more important to reliably pitch well in high leverage situations. I’ll call the high leverage pitcher the muscler/fireman. After the muscler/fireman is chosen, then the closer can be chosen. So, the revised questions are, “Who should be the muscler?, and “Who should be the closer?”
Let’s look at last seasons relievers for the Diamondbacks. Let’s screen out candidates who should not be the muscler or the closer.
First Screen: Candidates will be Diamondbacks relievers who pitched at least 30 innings last season. After that screen there were eight pitchers.