now, with the new rule that players can play in up to 4 games and still preserve their redshirt, I think that changes things dramatically in regards to playing true frosh. (I also think that it adds a huge and overlooked layer of planning/coordination/strategy in regards to how to use that rule - for example, if a frosh arrives late to fall ball or was injured or is behind on S&C, you can wait and play them in games later in the season when they're in better shape physically and with the playbook, if depth is thin at a certain position but a true frosh wouldn't get meaningful snaps on a weekly basis, maybe play him in a game or two early for him to get his feet wet and then save the other two games for the end of the season in case someone in the two deep gets hurt, etc)
here's who I think plays more than the 4 games and why:
QB Martinez - he wasn't their top QB target so that he could sit for most of the year leaving a redshirt frosh and a walkon as the two deep. If he doesn't win the starting job, he's the backup and is one injury away from the job, plus the staff wants to get him game reps even if he's not the starter
RB Washington - even though he was a surprise to be eligible, and has apparently lost weight while working on his academics, he's already impressing the defensive players in fall practice. I don't think that any of the other QBs have proven themselves to be "the man" heading into this season, and if Washington has a burst or speed that the other guys lack, I think the staff will give him a shot. Plus, they're going to be bringing in 2-4 RBs in the 2019 class and might want some separation. also, Washington seems to be talented enough that if he ends up being the start in a year or two, he might leave early for the NFL (yes way to early to speculate about that sort of thing but in this day and age someone who has the talent to possibly leave early imo you might as well play them and get their production while you can). I'm not impressed by Ozigo or Wilbon. I have no idea if Tre Bryant will ever be the player he was before surgery nor do I know how close he is to actually being game ready. Bradley got limited touches last season but I think has great potential. JUCO transfer Bell is my bet to get the start and the majority of the snaps, but I can easily see Washington working his way into getting regular snaps and by the end of the season possibly even being in the 2 or 3 deep due to his talent and speed.
RB/WR Jones - he wasn't recruited to sit. he was recruited to play the Duck-R position in SF's offense, and right now I think the only other players slotted in at that role are Lindsey and Spielman, and I have no idea if those two will also split time at a standard WR position or not. regardless, I'm pretty sure the kid is going to play.
S Jones - even though it now appears that safety has way more depth than we were expecting (A Williams, Reed, Domann, Dismuke, JUCO transfer D Williams, grad transfer Neal), 3 of them (A Williams, Reed, Neal) will be graduating, and 3 of them (A Williams, Reed, Domann) have an injury history. I also think we'll see juco transfer D Williams as the nickel DB a lot rather than at one of the standard safety positions. It's going to be tough to crack the two deep, but I think that Cam Jones is physically ready to play at this level and could be used on special teams and see mopup duty in some games or perhaps a lot of action if multiple players go down to injury during the season.
CB Taylor - players have been talking him up all summer based on his play in 7 on 7 work, and it continues in the fall. added to that is that the depth chart is paper thin at CB with frankly nobody really having performed well last season at all. I think he earns a backup job at CB and plays significant snaps all season
OLB Tannor - apparently he also arrived in good shape and ready to go physically. if he can demonstrate the ability to rush the passer in a way that other players currently on the roster cant, I can easily see him earning a job on special teams and as a third down pass rusher. there are tons of options at OLB, but nobody who's demonstrated the ability to be disruptive rushing the QB. I think he plays quite a bit.
TE Jurgens - if he's recovered from his leg injury and back in shape, I think he plays this year. NU really only has Stoll/Allen/Rafdal as TEs from the spring, and I think that SF and staff like a little deeper stable of TEs to be able to rotate some guys in and out to keep everyone fresh. I could see TE LeGrone playing as well, but not sure they need that much depth or if Legrone is as physically ready compared to Jurgens
WR McGriff - was here for spring ball and is a big tall target that really doesn't exist on the WR roster otherwise. I think he carves out a niche as a big target in the redzone and as a reliable option in the 3 deep that warrants him getting regular snaps. Morgan/Spielman/Lindsey/McQuitty cant catch all of the footballs.
K Pickering - he should win the starting job so, yeah, he's not going to redshirt.
I really don't see any of the others (OLB Alston, CB Clark, OL Farniok, DE Rogers, S Smith, WR Watt, DE Wildeman) either being physically ready to play, or where there is such a thin depth chart that they'd get meaningful snaps above and beyond the 4 games that the staff can try to work them in with.