Picking the Patriots’ 53-man roster just got more difficult. Here’s our projection

D.J. Foster is a jack-of-all-trades who can line up all over the formation as a receiver or running back.Eric Christian Smith/AP

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Choosing a 53-man roster for the Patriots just got more difficult.

It was easy when they had full health, when receiver Julian Edelman and defensive end Derek Rivers could be written in with pen.

But their knee injuries complicate matters for coach Bill Belichick. What to do with their roster spots?

The Patriots won’t necessarily look for 1-for-1 replacements. Undrafted rookie Austin Carr can’t just plug into the lineup and solve the Patriots’ riddle at slot receiver. And the Patriots aren’t going to find a productive pass rusher to replace Rivers at the bottom of their roster or on the waiver wire.

Belichick instead will look for the best football players to round out his 53-man roster, and figure out later how to make all the pieces fit.

The injuries will have a trickle-down effect on the roster. Suddenly, the Patriots need to find better depth with their offensive skill players. And they need to improve depth at pass rusher, especially after releasing veteran Kony Ealy on Saturday.

This could wind up being a year when the last two or three roster spots are filled by players who are in other camps right now. So take this 53-man roster with a grain of salt.

Following Friday’s preseason game at Detroit, and Edelman’s injury, here are our last ones in: RB Brandon Bolden, TE James O’Shaughnessy, OT Cameron Fleming, DE/LB Harvey Langi, CB Cyrus Jones, OT Conor McDermott, LB Trevor Bates.

And our first ones out: QB Jacoby Brissett, DE Geneo Grissom, S Jordan Richards, OT LaAdrian Waddle, LB Jonathan Freeny, WR Austin Carr.

Let’s break it down:

Offense (25)

Quarterback (2): Tom Brady, Jimmy Garoppolo.

We wrote on Sunday how Brissett didn’t play in the Patriots’ third preseason game, and how that was an ominous sign for previous No. 3 quarterbacks Tim Tebow, Ryan Mallett, and Ryan Lindley shortly before they were dumped.

Now with Edelman’s injury, the Patriots can’t afford to use a roster spot on a third quarterback who won’t see the field this year. They need help at receiver, defensive end, linebacker, and special teams.

Brissett has a place in the NFL, and he will be on a roster somewhere this fall. It just looks more and more as if it won’t be New England.

Running back (6): Mike Gillislee, James White, Rex Burkhead, Dion Lewis, Brandon Bolden, D.J. Foster.

It seems out of the ordinary to keep six running backs on the roster, but that’s a bit misleading. Bolden is really a special teamer who won’t take a snap with the offense this year, barring an injury disaster. We’re still not sold on Bolden claiming a roster spot, but Belichick loves his special teams ability, and he’s cheap, so he gets one for now.

Foster, the second-year player out of Arizona State, would be our in-house choice to replace Edelman. He’s a jack-of-all-trades who can line up all over the formation as a receiver or running back. The Patriots kept him on the roster all of last season, and clearly like him, even though he was a healthy scratch for 13 games. They gave Foster a ton of work against the Lions, and his versatility on offense, plus his skills as a kick returner, give him the nod over the Patriots’ other options.

Foster, Lewis, and White all are good pass-catchers and have experience in the Patriots’ offense lining up as a slot receiver.

Tight end (3): Rob Gronkowski, Dwayne Allen, James O’Shaughnessy.

It’s possible the Patriots go with only two tight ends, but O’Shaughnessy has two years of special teams experience, so we’re keeping him. He is a better athlete than Jacob Hollister, and gives the Patriots a decent red-zone option should Gronkowski or Allen suffer an injury.

Fullback (1): James Develin.

No debate here. Develin is a great lead blocker, plays on several special teams units, and will serve as a backup long snapper.

Wide receiver (4): Brandin Cooks, Chris Hogan, Malcolm Mitchell, Danny Amendola.

We chose Foster instead of elevating a fifth receiver. Carr, the rookie from Northwestern, has had a nice camp, and flashed some ability in the preseason opener. But he doesn’t quite have elite measurables, and looks like a better bet for the practice squad. Same goes for second-year receiver Devin Lucien, who also had a nice camp, but is more of an outside receiver, where the Patriots have good depth right now.

But don’t be surprised if the Patriots do find a fifth receiver on the waiver wire next weekend, or spring a last-minute trade before roster cuts.

Offensive line (9): Nate Solder, Joe Thuney, David Andrews, Shaq Mason, Marcus Cannon, Tony Garcia, Ted Karras, Cameron Fleming, Conor McDermott.

The losses of Rivers and Ealy gave us the room to keep McDermott, the rookie sixth-round pick who is a developing tackle. The Patriots have decent depth at tackle with Solder, Cannon, Fleming, and Garcia (who is dealing with an injury), but a team cannot have enough offensive tackles.

Fleming looks poised to beat out Waddle for the No. 3 tackle position, and Garcia and McDermott can be the emergency options.

Defense (22)

Defensive end (4): Trey Flowers, Deatrich Wise, Harvey Langi, Adam Butler.

The Patriots don’t necessarily need to sign another defensive end. In addition to the four players above, Dont’a Hightower and Shea McClellin will also help on the edge.

But the Patriots will likely scour the trade market and waiver wire for another body. They don’t have much experience on the edge right now, and it is unknown how a trio of rookies — Wise, Langi, and Butler — will handle the rigors of a 16-game season, plus playoffs.

Defensive tackle (4): Alan Branch, Malcom Brown, Vincent Valentine, Lawrence Guy.

This position is pretty well set. Guy and Butler have some versatility and can play defensive end or defensive tackle, depending on the situation.

Linebacker (6): Dont’a Hightower, David Harris, Shea McClellin, Elandon Roberts, Kyle Van Noy, Trevor Bates.

We’re not sold on Harris making this team. There is no question he is one of the smartest players in the locker room, and can be a leader of great character for this squad. But Harris also looked old and slow against the Lions, and could be viewed as a progress stopper for some of the Patriots’ younger defenders.

Harris is only a first- and second-down linebacker now, but that is also the role for Roberts, who is younger, cheaper, and packs a big wallop. For now, Harris makes the team, but he could be a surprise cut next weekend.

Bates and Freeny are battling for one roster spot, and we chose Bates, who is younger and cheaper. Bates, who played at the University of Maine, logged snaps with the starting defense on Friday, and has special teams ability. So does Freeny, but his salary is $1.2 million more than Bates’s.

Cornerback (5): Stephon Gilmore, Malcolm Butler, Eric Rowe, Jonathan Jones, Cyrus Jones.

Cyrus Jones, last year’s second-round pick, was one of our cuts a couple of weeks ago, but he has done enough recently to earn one last chance. He is fast and scrappy and can help cover the slot. Although he still needs work on his decision-making as a punt returner, his skills are needed more now that Edelman is out for the season.

Safety (3): Devin McCourty, Patrick Chung, Duron Harmon.

Not much to debate here. None of the Patriots’ three undrafted rookie safeties have made an impact. It doesn’t look as if they will stick around.

Special teams (6)

Kicker: Stephen Gostkowski.

Punter: Ryan Allen.

Long Snapper: Joe Cardona.

Other personnel: Matthew Slater, Nate Ebner, Brandon King.

Even with Gostkowski missing an extra point against the Lions, the Patriots won’t find a better kicking option on the waiver wire. They will have to ride it out with Gostkowski, and hope he can overcome his extra-point yips.

Slater and King have been injured throughout most of camp, which bears watching. If they are not ready to go for Week 1, Belichick will have to find other players to use on special teams, which will affect the decisions on the bottom of the roster.