First, all of them are failed starters. This usually implies a couple of things:
1. Not great control
2. Only two above average pitches
3. Really violent deliveries
The sample sizes for evaluating relievers is tiny. I mean a couple of bad appearances blows up most of your stats for the season. It's hard to find a lot of year to year consistency. I mean Ryan Brasier was just some random name the Sox found and he has been terrific. But he could very easily stop. Okajima was unhittable for a season and then stopped. Keith Foulke was heroic and then his arm fell off. There are a few good ones, but for the most part it's all context dependent.