Just to be clear, the Red Sox are 20-3 in games in which Bailey has made an appearance. They are 3-0 in games where he's blown saves. He's had 4 Holds and 8 Saves in 15 chances (80% success rate). League average Save % is 70%.
On the flip side, there is a some compelling evidence that shows that if you're not comfortable with Bailey, you need to look externally.
The cast that the Red Sox have put together in the bullpen thus far have converted just 13 of their 22 Save Opportunities. That's a 59% Save Percentage, and 9 blown saves. That's good for 26th in the MLB.
So, for those thinking that there would be a seamless transition to Miller, Tazawa, or Uehara, those numbers may surprise you a bit.
Now, Hanrahan was responsible for 2 of the BLSV and 4 of the Saves, so taking his numbers out actually enhances the problem. Without Hanrahan, the Sox have converted 9 Saves in 16 opportunities (56.25%).