Stammen's loss was pretty huge, though I don't think anybody was really thinking about him going into the season, he looked fantastic to start the year, and his absence has suddenly magnified an already worrying problem.
I agree Thornton should be getting more innings, particularly as part of the "A" bullpen. Make him the full-time setup man. His splits are absolutely fine.
The problem with Treinen (and unfortunately, I believe it's the same problem with Roark) is that lefties crush them - both have an OPS of over 1000. This is why I don't think switching Treinen for Roark will make a huge difference, except that Roark has perhaps a better mental makeup and more big league experience, so perhaps he will just pitch around lefties.
Barrett is 27, if he's a project he's going to be a late bloomer and be Thornton in ten years. He's likely just going to be Mitch Williams, effectively wild. How'd that work in 1993? Martin, Rivero, Grace - who knows what they're worth. Same goes for Janssen, track record be damned, he had a weird second half last year, has declined in years and is starting the year with injury.
I like the idea of getting Papelbon or Chapman - we really never know what we have with Storen. Papelbon is still fantastic, google "Papelbon" and read the first story that pops up, written today for MSNBC. Chapman would probably be cheaper just because Amaro is a madman, and the Reds are likely dealing him and Cueto come July.
I think the team is okay as it is, I have confidence in them taking the division as soon as the Mets' problems catch up with them. But we're not talking about the regular season, everyone here is expecting great things, and both times we've missed our chance due to bullpen issues. So this feels like a pretty big problem.