I like Atkins but there's a lot of questions. At his price it's keeper or bust which means you're needing him to hit 105+ barring a big drop in the premium level. He's a good player but that's a big leap for a player who to date has rarely hit that level, ultimately he's a solid player and will definitely watch his role with Selwood retirement and the aging of other guys but definitely need to see something, just a super awkward price.
Sinclair the concern is definitely Lyon for mine but also that he started to get attention late last year and I expect that to continue. Mostly though we just don't know what the strategy will be, traditionally Lyon's teams do produce high scoring defenders, some of the highest we've seen, but will need to see that role there and that he has it. They've got Coffield likely returning, who definitely overlaps, NWM allegedly also playing as a rebounding defender and a couple of others that can also intercept that Lyon may prefer in that part of the role.
At his price I think there's a lot of merit to waiting to see if Sinclair is worth that price, I think the upside is pretty limited so you want to be damn certain of his scoring and, in all honesty, I think that Sicily, Stewart, Dawson and Docherty all present safer bets given their more proven scoring history and, in general, role certainty. Don't think the idea that Sicily is the top defender again is a bad call at all but I think there's a pretty strong case for him not being it also and generally at that price range the one thing you shouldn't have is uncertainty.