IP W SV BB K ERA WHIP are the pitching categories.
SP, SP, RP, RP, P, P, P, BN, BN, BN are the pitching slots.
For this league, closers help you with saves, and a little in K/ERA/WHIP. Would it be better to just go with 2 more starters? So with 0 relievers, you should win IP/K/W and lose SV/BB vs someone with 2-3 RPs. Then you can still probably win ERA/WHIP if your starters are much better due to not having any RPs.
So the way I see it, in this league setup, having no RP will lose you saves, but with the daily update of SPs you'll probably win at least 2-3 cats just from a starting pitching edge. If you look at average Ks/IP/Ws for starters, having 3 more starters should ensure those 3 cats and at most you lose SV/BB. I think the key is daily updates. If you can rotate in 3-4 bench SPs, thats 30-40 more innings, 2-3Ws maybe 10+Ks. With the daily update, any effect RPs have on whip/era is severely reduced. So they might, or might not win you 1 category.
I currently have Rivera and Isringhausen. I'm thinking I can 1 stud SP and some hitting help.