I think that you must have some notion/ theory/ formula about hitter/ pitcher equivalency and, if Santana/ RJ/ anybody depending on the round are there when it's your pick, you have to take them.
I just drafted yesterday and the SP are a bit shaky(Harden, Bondermann, Oliver Perez do you see a trend?

) but I have Borowski, FRod and 3 top MR (we use holds in our goofy format but, for some reason, perhaps 'postional drafting', looking to fill roster spots w/ 'backups'

) the other managers just ignored my move into that field so I got Gordon/ Rincon AND Otsuka

although the guy after me said 'Rincon' 2 picks after I had him and was SURE he'd grab Otsuka too.
I've done two drafts so far and, in both of them, I was able to get SP/ RP I wanted that were left on the board b/c everybody else has apparently read the 'Offense before defense' stuff and have gotten some nice deals on guys who appear likely to put up #s pretty late in the drafts I've been in. We'll see I suppose. I think though that it's a mistake to stick to a theory if there's a guy up who is the best player. Theories are good but you have to have some flexibility since you never really know what's going to fall in your lap. Then, you have to follow up w/ adjustments to make sure that you don't get left out w/ a weak spot.