Being a mainstay on the Patriots for many years now, Rob Ninkovich has been sort of a "jack of all trades" type of player for the team. He served as both an inside and outside linebacker earlier in his NFL career before moving to the defensive end as a primary pass-rusher, where he has been for several years now. He even was a long-snapper for a game in 2014 for the Patriots as well.
But earlier this summer during mini-camp, Ninkovich was seen practicing as an inside linebacker for the team in their 4-3 defense. Since then, he has primarily been taking reps at his normal defensive end position. When hearing about Ninkovich's injury, most would think that this would put the defensive end position in jeopardy. But in reality, it affects the inside linebacker depth more so for the Patriots.
The Patriots have two bonafide superstar linebackers with Jamie Collins and Dont'a Hightower, but unfortunately have a shaky situation behind them at the linebacker position. Collins is more of an outside linebacker while Hightower is an inside linebacker, where the problem lies. Behind Hightower, the team is lacking solid inside linebacker depth. Ramon Humber and Elandon Roberts would be the next two to step up if something were to happen to Hightower.
Humber is a nine year veteran who spent the last six season with the Saints before signing with New England this past off-season. Humber was seen as more of "key" back-up inside linebacker rather than a starter while with New Orleans and is expected to have the same sort of role with the Patriots. Elandon Roberts is a sixth round draft pick out of the University of Houston who led the NCAA in solo tackles in 2015 but, like Humber (5'11", 235 lbs), is undersized to play the position ideally (6'0", 235 lbs).
Both either have little or no experience as a starting inside linebacker in the NFL and would be a big drop-off in talent from Hightower. Jonathan Freeny is also someone who could play inside linebacker in an emergency, but is better suited as an outside linebacker in the Patriots 4-3 defense. With Ninkovich, he had years of experience playing both inside and outside linebacker while being more adequately "built for the position" at the 6'2", 260 lbs. As NESN.com's Doug Kyed wrote back in June: "The 32-year-old defender had 6.5 sacks last season, but he could provide stout run defense in the middle of the Patriots’ defense if the move is permanent."
The Patriots had essentially been trying to use Ninkovich not only as one of their primary pass-rushers but as a back-up run-stopper in the middle on early downs. With Ninkovich out for the near future, the team is "back to square one" with that game-plan. As mentioned previously, the team was already dealing with depth issues at inside linebacker and now have to adjust with losing their "emergency linebacker". Luckily, the defensive end position is not one that is dealing with same issue.
The defensive end position is rather well-equipped with depth after the team brought in Chris Long this past off-season, drafted Trey Flowers and Geneo Grissom last season and signed Jabaal Sheard last off-season. Long is a steady veteran who has put up several terrific seasons with the Rams and still is a solid veteran presence to have. Flowers (4th round) and Grissom (3rd round) were selected last season and were both expected to have bigger roles coming into 2016 already.
Flowers showed well in the 2015 pre-season before missing a lot of time due to a knee injury. And while Grissom played mostly on special teams in 2015, he has a very high ceiling and is extremely athletic. There is reason to believe Grissom could do well in 2016 now that he progresses into his sophomore year in the NFL. And Sheard has proven to be a highly-effective player who may not have even reached his peak yet. So while losing someone as reliable (42 sacks in the past seven seasons) and durable (has not missed a game in six seasons) like Ninkovich is a tough pill to swallow, the team has at least some depth behind him to soften the blow.
Someone else to mention is Shea McClellin, who was signed this off-season from the Bears to a three year contract. McClellin has experience as both an inside and outside linebacker along with defensive end as well. As Providence Journal's Mark Daniels wrote: "During his time in Chicago, he studied Ninkovich and now McClellin looks like a logical replacement." With Ninkovich turning 32 years old back in February, McClellin was signed to most likely replace him one day and that may come earlier than expected. McClellin was inconsistent at times in Chicago, but the Patriots clearly have faith in him after they gave him a three year contract. With McClellin now most likely thrust in Ninkovich's role for the time being, how he steps up and handles it will be key for the Patriots defense.
Going back to it, Patriots clearly have a depth issue at inside linebacker that needed to be fixed even before Ninkovich's current injury. The free agent pool at inside linebacker is very uninspiring as DeMeco Ryans, Curtis Lofton, Joe Mays, Desmond Bishop and Casey Matthews are considered to be the top free agents. But knowing the Patriots, they will be scouring around as we get closer to the regular season and roster cuts have to be made.
It's very possible that the team waits to see who is released/cut and try to sign someone(s) who could fit the bill of a 4-3 inside linebacker. It also isn't out of the realm of possibilities that New England could try to swing a minor trade for a late round/conditional draft pick, as we have seem them do it before at varied positions.
To summarize, Ninkovich's injury is a tough one to deal with due to his consistent production and presence on the field, helping to lead the defense. While he may not miss the entire season or even have to be put on the PUP list if the reported timeline for his recovery is correct, his effect spreads to more than just one position and it'll be interesting to see how the team reacts following this discovery about his injury.