Accrued seasons and basic PS eligibility rules:
In order to understand practice squad eligibility rules, you have to know what "accrued seasons" toward free agency are. To accrue a season, a player has to be on an NFL regular roster of 53, an inactive PUP list (regular season version of PUP) due to an NFL football related injury, or an IR list for at least 6 regular season games. Players who have not already "burned through" their up to 3 seasons of PS eligibility, clear waivers, and have zero accrued seasons, or have been on a game day active roster of 46 for no more than 8 games during the accrued season or seasons they have accumulated toward free agency are PS eligible. A team may also sign up to 4 out of 10 players to their PS who have no more than 2 accrued seasons, regardless of how many regular season games they were on an active game day roster of 46 ("special" PS slots). So basically any player who was drafted or signed as a CFA in 2015, 2016, or 2017 is potentially PS eligible if he gets waived and clears waivers.
Effect of previous PS experience:
To determine the potential PS eligibility of former PS players, it is necessary to determine how many seasons of PS eligibility they have "burned through." For the first 2 seasons of PS eligibility, a player "burns through" a season of eligibility by being on a team's or multiple teams' PS for 6 or more regular and/or post-season games. For a third and final season of PS eligibility, a player only has to be on any team's PS roster for one regular or post-season game. If he gets released from a team's PS during that 3rd season, he can be re-signed to that team's or some other team's PS that season, but he won't be PS eligible in future seasons.
Other PS rules and facts that may be of interest:
Current rules (2017) dictate that teams can have up to 10 players on their PS rosters. (Original rules only allowed for 8). Of those 10 PS slots, up to 4 can be used on any player with no more than 2 accrued NFL seasons ("special" slots) regardless of how many regular season games a player has been on a game day active roster of 46.
Players on the PS roster (for the 2017 season) get paid a minimum of $7200 per week (bye weeks count), for each regular season and postseason week they're on the PS roster, and it counts against the cap. There is no maximum allowed PS salary, but as I said, PS salaries count against the cap, so PS players are rarely paid more than the minimum.
If a PS player gets promoted to his own team's regular roster temporarily, and his team needs his roster slot, he must clear waivers again before he can re-sign with his current team's PS, or sign with any other team's PS.
PS players are "quasi" free agents. Team B can offer Team A's PS player a veteran's minimum salary contract for their regular roster of 53, and if the player accepts, team A just had their PS player "poached." However team B must pay team A's former PS player veteran's minimum salary for at least 3 weeks, and the player will take up one of team B's 53 regular roster slots for at least 3 weeks, even if he is released before the end of the 3 weeks.
Potentially PS eligible 2017 Broncos players:
On to the list of players who were on the Broncos' TC roster of 90 who will be PS eligible IF they clear waivers. I will omit players who are generally considered to be roster locks. I will list them by years of experience as provided on the roster at the Broncos's official site. An * indicates a player who is only eligible for one of the 4 "special" PS slots.
The true rookies:
Nelson Adams: DL. Signed after Billy Winn went to IR. Haven't heard squat about him since. Probably just a camp body.
Dante Barnett: S. Made a favorable impression on CHJ early on in OTAs, but I haven't heard anything about him since.
Jamal Carter: S. Has a very realistic chance of making the roster of 53. IF he doesn't, AND clears waivers, I absolutely want him on our PS.
Ken Ekanem: OLB. Probably not a candidate for the 53, but has a decent shot at a PS slot given our injuries at the position.
Jerrol Garcia-Williams: ILB. Haven't heard squat about him since the Broncos signed him
Carlos Henderson: WR. One of our 3rd round picks. Had some struggles adjusting to our offense, and hasn't practiced or played since the first preseason game due to a ligament injury in his thumb that required surgery. I expect he'll go to IR during roster cuts.
De'Angelo Henderson: RB. 6th round draft pick. Is there anyone who doesn't believe this kid has earned a roster slot? Highly unlikely he'd clear waivers to PS IMO.
Deon Hollins: LB. Undersized LB who was a decent pass rusher in college, but lacking in coverage skills. I had to root for the kid because he took the time to introduce himself to MHR, but I'll be surprised if he has a future with the Broncos.
Cameron Hunt: OG. Haven't heard squat about him.
Tyrique Jarrett: NT. Greatly exceeded my expectations, and has a shot at a roster slot, especially given our DL injuries. If he doesn't make the roster, I definitely want him on our PS IF he clears waivers. He might. 0 technique NTs aren't valued particularly highly around the League currently.
Anthony Nash: WR. Great length and speed for the position, but hasn't impressed during TC.
Marcus Rios: CB. "Can't make the club from the tub."
Kyle Sloter: QB. If you don't know anything about his situation by now, I can't help you.
Shakir Soto: DE. I've seen a little positive press about this guy, so I'll call him a "maybe" for PS, especially given his positional value and our injury situation.
Orion Stewart: S. Hasn't made as strong an impression as Jamal Carter, but he's had a good TC.
Dymonte Thomas: S. Ditto what I said about Orion Stewart, but probably to a lesser degree.
Elijah Wilkinson: listed at OT, but I seem to remember him getting a TC "attaboy" at OG. Might be a developmental OL worthy of a PS slot.
Stanley Williams: RB. Signed late to replace the injured Bernard Pierce. Small, speedy scat back type, and the only RB on our current roster i see as a realistic PS possibility.
The first year players (not true rookies, but have not yet accrued a season):
Dillon Day: C. A bit undersized for an NFL OL, and his best fit is probably at C in a ZBS since he doesn't appear to have OG versatility. He's already spent 2 seasons on the Broncos' PS, and it's rare for them to keep the same player for a 3rd.
Cedrick Lang: OT. Long, tall, former college basketball player who switched to football and played TE as a 5th year senior, and went through TC with the Giants last year after signing as a CFA. Interesting developmental project with emphasis on the word "project."
Justin Murray: OT, Spent the 2016 season on the Broncos' PS. Maybe he'll get a 2nd PS year.
Steven Scheu: TE. Signed to the Broncos' PS on 10/19/16 after having been signed as a CFA and gone through TC with the Patriots.
Hunter Sharp: WR and kick returner the Broncos showed some interest in prior to the 2016 draft. Began his NFL career as a CFA with the Eagles, and was signed to the Broncos' PS on 12/28/16.
Austin Traylor: TE. Signed as a CFA with Dallas, and then bounced around from one PS to another until he landed on Denver's on 12/20/16. He appears to be an H-back, type who can fill in at FB occasionally as well. MHR resident draft guru Dr.Cyanide believes the Broncos are high on this kid, so I'd guess he has a pretty good shot at a PS slot. Maybe he'll be Virgil Green's younger, cheaper replacement assuming Green walks away in free agency in 2018.
The 2nd year players:
Zaire Anderson*: ILB. Signed as a CFA in 2015, and spent the entire season on the Broncos' PS. Made the roster in 2016, and was active for every game, starting 1.
Vontarrius Dora: OLB. Signed by Denver as a CFA in 2016, and spent the first 13 weeks of the season on PS before getting promoted to the regular roster. Dark horse candidate for a roster slot this year due to injuries at the position, but PS is a more likely possibility.
Quentin Gause: LB. Started his NFL career as a CFA with the Eagles. Spent time on their PS and then New England's before signing to the Broncos PS roster on 10/19/16. Was promoted to the active roster on 12/10/16, and played in 3 games. I don't know if he's the developmental ILB the Broncos want, but they need to be developing somebody at ILB on PS this year since both Todd Davis and Corey Nelson are scheduled to hit free agency in 2018.
Andy Janovich*: FB. He's making the 53. Enough said.
Paxton Lynch*: QB. He's making the 53, even though there are a few fans who are ready to waive him.
Danny Mason: OLB. Began his professional football career in the Indoor league in 2014, Went through 2015 TC with the Broncos, and began that season on their PS. Got waived, and ended up spending the rest of the 2015 season on the Bears' PS. Went through most of 2016 TC with the Bears, got injured, and spent the season on their IR. Was signed for the Broncos' 2017 TC due to injuries to Ray and Barrett.
Will Parks*: S. I think he's making the roster, but some people aren't convinced. He would be eligible for one of the special slots if he cleared waivers.
Kyle Peko: NT. Spent most of TC on PUP after fracturing a bone in his foot during minicamp at the end of OTAs, but was recently activated. He's a dark horse candidate for a roster slot as the backup NT behind his cousin Domata Peko, and a definite PS candidate if he doesn't make the roster. He has adequate athleticism for the DE position as well, but lacks the desired length.
Kalif Raymond: WR and returner. He's small, but he's fast and he's quick. Signed with Denver as a CFA in 2016, and spent most the season on PS, but got promoted to the regular roster, largely due to Jordan Norwood's ineptness as a punt returner, and played in 4 games. I think his chances of making the 2017 roster were doomed from the moment the Broncos drafted McKenzie, but he's had a good TC, and I'd love to keep him on PS IF he clears waivers.
Kevin Snyder: ILB. Signed with Detroit as a CFA in 2015. From there, his NFL history gets hard to follow, since he's spent time on IR lists. practice squad lists, and was even briefly on the Patriots' regular roster. Suffice it to say that he's only accrued one season, and is PS eligible for any of the 10 slots if he clears waivers.
Jordan Taylor*: WR. Signed as a CFA with Denver in 2015 and spent that season on PS. Made the roster in 2016. Considered to be a roster bubble player this year, but IS eligible for one of the special slots IF he clears waivers which I think is highly unlikely. If he doesn't make the roster, the Broncos will lose him.
The 3rd year players:
A.J. Derby*: TE. 2015 6th round draft pick by the Patriots who spent his rookie year on IR. Acquired by the Broncos shortly before the 2016 trade deadline for a 2017 5th round pick. I'm pretty sure he's making the roster.
Lorenzo Doss*: CB. 2015 5th round pick by the Broncos. The kid has some real ball hawking talent, but also has shown a tendency to blow his coverage responsibilities while trying to make "big plays," and I believe that's a major reason why he's a roster bubble guy for the Broncos. I doubt if he can clear waivers, but he would be eligible for one of the special PS slots if he does.
Bennie Fowler*: WR. Signed with the Broncos as a CFA in 2014, and spent his rookie season on PS. Made the roster in both 2015 and 2016, and got significant playing time. The coaches seem to think much more highly of his skills as both a receiver and a special teams player than many of the fans do, so I believe he's almost a roster lock.
Max Garcia*: OG. Don't think I have anything to add to what has already been said about Garcia. Sounds like the coaches have higher hopes for him than many of the fans do, and like it or not, he's probably making the roster. Please, somebody, make a trade offer Elway can't refuse!
Jeff Heuerman*: TE. 3rd round 2015 Broncos' draft pick who tore his ACL in rookie minicamp, and spent the entire 2015 season on IR. Had a largely disappointing 2016 season, but I seem to recall that health was questionable early on. I believe he'll make the 2017 roster, but I'll probably be ready to give up on him if he doesn't produce this year.
Deiontrez Mount: LB. We just signed this guy, so I know very little about him. He was a 6th round draft pick by the Titans in 2015, played 4 games for them, and ended the season on their IR. In 2016 he spent time with the Colts on their PS and active roster both. Looks like he's only played in 5 total games between the 2, so he does apparently have potential PS eligibility.
Ty Sambrailo*: OL. Not much to add to what has already been said about this guy in other posts. I do find it interesting news that he's taking some practice reps. at center.
4th year players and beyond: None of them are PS eligible.
Hope this post will serve as a useful reference, and also spark some lively discussion with roster cuts and practice squad assembly rapidly approaching.