By Matthew Geagan, CBS Boston

BOSTON (CBS) — Leading up to the 2021 Patriots season, we’ll be taking a look at a specific storyline that will have our attention throughout the season. Today we take a look at one area of the defense that is starting the season with a gigantic question mark: How will New England’s corners fare without Stephon Gilmore?

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Gilmore is starting the season on PUP as he recovers from the quad injury that ended his 2020 season early. He’s also pining for a new deal from the Patriots, so it’s fair to say this is an injury absence/contract holdout from the veteran corner. It’s unfortunate, because Gilmore’s addition to the rest of the defense could make the unit a special one.

Without Gilmore, there are some major questions regarding New England’s corners. His absence leaves the unit without one of its best playmakers — or their best player at keeping plays from happening. Even if there are questions about what Gilmore will be coming off a quad injury at the age of 31, his presence is still important in the secondary. Without Gilmore there is a trickledown effect on the rest of the unit.

J.C. Jackson will slide into Gilmore’s top corner role to start the season, which he filled to some mixed results in 2020. Jackson came down with a career-high nine interceptions last season, and was able to keep opposing receivers from breaking off too many big gains. But he also surrendered a completion percentage of 59 percent when he was targeted, which is not ideal from a top corner. But he’ll be playing for a big payday in 2022, so he’s got plenty of motivation to continue his ascension to All Pro status.

The bigger question mark is opposite Jackson, with newcomer Jalen Mills taking over in the No. 2 corner spot during Gilmore’s absence. After he struggled in that role during the preseason, teams are going to lock into Mills to start the season. A lot. It’s a matchup everyone is going to look to exploit while they can, and will no doubt lead to some frustrating days for the defense.

Just imagine what that Buccaneers quarterback is going to do against a patchwork secondary in Week 4. It could get ugly that particular Sunday evening in Foxboro.

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To make matters worse, Mills missed practice on Thursday, putting his status for Sunday’s opener against Miami in doubt. That will just further complicate the issues at corner, with third-year defensive back Joejuan Williams next in line to start opposite Jackson.

With an improved defensive line that will actually be able to stop the run, plus a pretty scary pass rush, cornerback appears to be the weak link on the New England defense heading into the season. Jackson and slot corner Jonathan Jones are both solid, but the overall play of the corners will be a big question mark until Gilmore gets back — if he returns at all without a new contract. If Gilmore ends up elsewhere and isn’t part of the mix at all, the Patriots will have to rely heavily on Mills, Williams and Shaun Wade to fill the void.

The uncertainty at corner is going to trickle down to the rest of the defense. More pressure will be on the line to stop the run, and even more pressure will be on the team’s pass rushers to force quarterbacks into making quick decisions — and send them to the ground a number of times every Sunday.

The Patriots should still have one of the NFL’s top defenses, even with a subpar collection at corners. It’s going to be a lot harder to shut down offenses without Gilmore in the mix, though  the other defensive groups playing to new levels should be able to make up for his absence.

But it’s not something the Patriots should plan on happening for a full season, not if their goal is to control every game with a strong run game and stellar defensive play.

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Tune in to Patriots-Dolphins on Sunday, Sept. 12 on WBZ-TV — the flagship station of the New England Patriots! Coverage begins Wednesday night with Patriots 1st Down at 10:30 p.m. on TV38 and continues Friday night with Patriots All Access at 7 p.m. on WBZ! Our opening day coverage begins with Patriots GameDay at 11:30 a.m., the Patriots and the Dolphins kick off at 4:25 p.m., and after the game switch over to TV38 for full reaction and analysis on Patriots 5th Quarter!