The following are the the potential Jays relievers and their wOBA splits compared to the league average wOBA splits. Data is taken from 2010-2012.
Full disclosure: I stole this idea from this post on The Process Report, but I changed a couple of things. First, it looks like R.J. compared right handed pitcher splits only against other right handed pitchers, while I'm comparing to all pitchers, because I think that gives you a better indication of how the pitcher did compared to league average (and also it was easier for me to find the information.) I'm also using wOBA against, whereas R.J. used OPS against. And like R.J. says in that post, it would be better if these numbers were park adjusted, but he didn't do that, so neither did I. I've also included innings pitched, so you can get an idea of the sample size.
On to the numbers:
|RH wOBA-||LH wOBA-||RH IP||LH IP|
So the top three in the pen are all above average against both right handed batters and left handed batters. Janssen and Santos both actually have reverse splits, in that their wOBA against is lower against left handed hitters than it is against righties. Oliver is very effective against both.
Delabar has a reverse split as well, showing a well above average split against lefties, while struggling against right handers. (If you only include Delabar's numbers with Toronto, when he stopped throwing the slider and increased his usage of the splitter, he has about an 84 wOBA- against RH hitters)
Lincoln's splits are both below league average, but that also includes his time as a starter. Last year, Lincoln was much better against left handers, with an 83 wOBA-, but still had a 109 wOBA- against right handers.
For the second lefty in the pen, the Jays have to choose between Aaron Loup, Brett Cecil and J.A. Happ. When you look at the splits, I think it's clear that Loup is the best option. He has the least experience of the group, with only 30 major league innings, but in that time he's been good against batters than hit either way. Cecil on the other hand, has a nice 80 wOBA- against lefties, but with a 115 wOBA- against right handers, it's clear that he should only be deployed as a lefty specialist, while with Loup you at least have some hope that he can handle right handed hitters as well. Happ also has been poor against RH hitters, and when you consider that he's the Jays 6th starter, I don't see any benefit of having him in the bullpen.
Esmil Rogers' splits look pretty ugly all around, but that includes his Colorado time, when he was awful. If you only include his time with the Indians last season, he's at about 87/90 for RH/LH.
All in all, this should be a very effective bullpen against left handed hitters in particular. There'll be two lefties, plus at least 3 right handers that have shown reverse splits. Probably not going to be as effective against right handers, but should be more than adequate. And they've gotta be better than Francisco Cordero - right?