The single biggest concern facing the 2023 New England Patriots got even bigger Friday night.

Offensive lineman Riley Reiff exited the Patriots’ final preseason game — a 23-7 loss to the Tennessee Titans — after teammate Sidy Sow landed on the side of his right leg. The 34-year-old was evaluated in the sideline medical tent, walked off toward the locker room at Nissan Stadium and wasn’t seen again.

The severity of Reiff’s injury remained unclear as the game ended and the Patriots prepared to fly back to Foxboro, Mass. But it was the latest example in a troublesome trend that threatens to undermine Bill O’Brien’s otherwise promising new offense.

With final cuts forthcoming, the Patriots have a total of 16 offensive linemen on their 90-man roster. After Friday night, seven of them — nearly half — now are dealing with some sort of injury.

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A rundown:

Mike Onwenu
Underwent offseason ankle surgery, missed the entire spring and spent nearly all of training camp on the physically unable to perform list. Returned to practice Wednesday, but only in a limited capacity (left the main practice field before team drills).

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Cole Strange
Suffered a knee/leg injury in the first live-contact drill of training camp. Has been present at several practices over the last two weeks but has yet to take any competitive reps since his injury.

Calvin Anderson
Spent all of camp on the non-football illness list. Watches most practices in a sweatshirt, hood up. Has not suited up since minicamp.

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Conor McDermott
Suffered an injury in the first joint practice with the Packers and hasn’t been spotted since.

Kody Russey
Suffered an injury in the first preseason game and hasn’t practiced since, though he has attended some practices in uniform.

Atonio Mafi
Seemingly was a full participant in both practices this week but did not dress for Friday’s game.

Riley Reiff
Left Friday’s game with an apparent knee/leg injury.

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That list includes two no-doubt starters — Strange at left guard and Onwenu at either right guard or right tackle — plus potential ones in Reiff (at whichever spot Onwenu doesn’t play) and Anderson.

McDermott also repped with the top unit for much of training camp before being demoted shortly before his injury. Mafi likely would be the next man up at left guard if Strange isn’t ready to go Week 1.

Who’s healthy? Most importantly, starting left tackle Trent Brown and center David Andrews, both of whom got the night off on Friday. Veteran backup James Ferentz is injury-free, too. Beyond them, it’s a collection of young players with zero regular-season NFL experience: rookies Sow, Jake Andrews and Micah Vanterpool; second-year pros Chasen Hines and Andrew Stueber; and longtime practice squadder/converted defensive tackle Bill Murray.

Sow, another potential starter at right tackle, is playing that position for the first time since 2018, having exclusively played right guard for his final four years at Eastern Michigan.

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All of this becomes even more worrisome when you look at the Patriots’ schedule and see that their Week 1 opponent is the Philadelphia Eagles, who sacked opposing quarterbacks 70 times last season (tied for third-most in NFL history) en route to a Super Bowl appearance.

The Patriots’ patchwork O-line struggled even against backups this preseason (six sacks allowed Friday night). Things need to change, and quickly, for it to have any chance against that vaunted Philadelphia front.

The good news is Onwenu and Strange appear to be getting close to returning, which would give the Patriots at least four-fifths of their preferred starting line. It’s still not clear what their plan is at right tackle — which isn’t ideal two weeks out from the start of the season — but O’Brien is a skilled enough play-caller to scheme around one O-line weak spot.

There’s no guarantee either of those injured starters will be cleared in time for the season opener, though, and even if they are, it could take some time for them to work their way back after weeks or months on the shelf. After seeing how poorly many of its reserves performed this summer, New England needs to strongly consider calling in reinforcements in the form of late-summer trades or cutdown-day waiver claims.

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The Patriots left themselves little margin for error this offseason when they eschewed big-name free agent tackles for mid-level signings and early-round prospects for Day 3 fliers. This wasn’t a group built to withstand a rash of injuries. The success of O’Brien’s offense could hinge on how well it responds.

Featured image via Eric Canha/USA TODAY Sports Images