This really isn't so much a 53 man guess as it a breakdown of positions, spots,and who's competing for them. I'll start with the offense (will follow up later on defense). This is all assuming health, which no one is ever 100% healthy.
QB (2-3 spots): Smith is a lock. McCoy seems to be a near lock, though I suppose there's the ever small chance Hogan balls out and convinces the team to move on from McCoy. Hogan seems like the back-up plan for next year (when McCoy's a free agent). So I suspect Hogan makes the 53 unless he plays he way off. Which is also possible. There's literally no one else in competition here.
RB (3-4 spots): The two locks here seem to be Guice and Thompson. I know the team hopes Guice becomes the bona fide starter too, which should happen. But he'll make the team regardless. Thompson will do his thing as more of a "third down" type back. Perine should be the main back-up. He did not have a good rookie season, but got most of his playing time after the offensive line fell apart. So I'd give him a bit of a pass. Rob Kelley is the other main competition for the back-up job. If Perine beats out Kelley, I suspect Kelley gets cut. He could make it as a fourth RB, but someone like Bibbs seems more useful given his special teams/pass catching. There's a few other RBs in camp: Keith Marshall, Byron Marshall, and UDFA Martez Carter. All seem like extreme long shots. Oh yeah, and one fullback, Wellman. Who's probably at best a practice squad candidate.
TE (3-4 spots): Although there are 5 bodies in camp, this seems extremely likely to end up with 3 names on the final 53: Reed, Davis, and Sprinkle. There's upside there. But down side too. If Reed gets hurt, David shows his age, and Sprinkle fails to develop, there's a gaping hole on the roster. And the only other two bodies in camp are an unheralded UDFA (Flanagan) and a former UDFA (Garner). Both seem like practice squad at best types.
WR (5-6 spots): Richardson, Doctson and Crowder are the 3 locks, though all come with questions too. Like TE, if things go poorly then this position thins out fast. There's at last 2 additional spots to be won. the team re-signed Quick, though he basically did nothing last year and would seem to be more of a back-up plan. Harris is former UDFA and has been cut twice in two season. But he manages to find his way back. So he might make it, but it seems 50/50 at best. Robert Davis was the only draft pick would failed to make the 53 last year. But he was always seen as a developmental pick. So maybe he steps up. The team largely ignored WR on draft day, using only the last selection in the draft on Trey Quinn. He and UDFA Simmie Cobbs seem like the best bet among rookies. Though there are 4 other UDFAs on the roster (Sims, Holder, Fields and Pierson-El) to try and impress.
OL (8-10 spots): Let's start with the locks: Williams, Nsekhe, Roullier, Moses, Scherff, and Christian. Given the injuries here and the fact many project Christian to need a year or two, then I suspect at least 9 players make the final 53. But the question is who after these 6? Lauvao is back, but without a big contract and with a history of injuries and poor performance. Some seem to favor Kouandjio as the potential LG starter, but this is a guy the team cut last September. Catalina was an UDFA, but made the 53 last year. Kalis did not, but is probably a better pure guard and the team went out of their way to claim him back. Some like Bergstrom, but he was a street free agent the team signed once everyone else got hurt. I'd suspect the team would generally go younger, if those players are semi-decent. Clemmings is another name to consider. And then two highly ranked UDFAs in Welsh and Parris. Plus several other camp bodies in Balducci, Jefferson, and Kling.
That's it for offense. Defense to come, but we'll knock out special teams while we're here:
ST (3 spots): People basically expect Sundberg, Way, and Hopkins to take them. No real discussion needed