I don't know what the Cubs' plans are for Kilian or Brown, but before he got hurt, Kilian was dealing. He has the pitching repertoire to be a starter if he can throw strikes and has the potential to be a good one. I think Brown's repetitive movement neck injury thing or whatever makes him very unlikely to become a starter, but if he could... Needless to say, he also has the makings of a late inning guy, so if he is healthy, they have a pretty strong pen with all the other additions.
I do tend to worry more about Shota and Steele taking a step back and putting more pressure on the pen. And I also worry about the brutal April and early May schedule taxing the pen until the ASB.