The timetable for his return was given by head coach Doug Marrone via the team's official Twitter account, and according to Rotoworld, ESPN's Chris Mortensen said on NFL Insiders "maybe Week 6 in a best case scenario" in regard to when the second-year defensive back may see the field again.
Gilmore, who struggled early as a rookie but flashed shutdown abilities in the latter stages of 2012, was primed to start the season as the "Darrelle Revis" of Mike Pettine's defense.
Now, Rex Ryan's former right-hand man faces another long stretch of games without his top cornerback.
How will he adjust? Let's use history as guide.
52.4 percent in '09 (first in NFL), 44.7 percent in '10 (third), 32.8 percent in '11 (12th) and 34.0 percent in '12 (11th)
Remember, Revis had six interceptions in 2009 and earned his first All-Pro distinction. The following year, he missed three games and didn't have a pick but allowed only 22 receptions on 57 targets according to Pro Football Focus (subscription required).
Basically, Ryan—who was the sole defensive play-caller at that point—had the league's most suffocating man-to-man cornerback at his disposal, which may have lead to a higher frequency of blitzes.
It's almost impossible to gauge whether Pettine will dial up more or less blitzes with Gilmore gone.
Due to the lack of depth at cornerback, blitzing between 45-55 percent of the time seems foolish, but 30-40 percent is logical and would still be significantly more "blitz-happy" than Dave Wannstedt's ultra-vanilla system of a year ago.
According to Pro Football Focus, Buffalo blitzed on only 17.4 percent of its defensive snaps last season.
While Pettine probably can't take as many risks—or will shy away from sending as many blitz packages—with Gilmore sidelined, he does have quite the talented defensive front.
Kyle Williams, Marcell Dareus and Mario Williams fell short of expectations in 2012, but Wannstedt rarely moved the three tremendous athletes, utilized line stunts or zone blitzes.
Pettine can get creative with that trio and up-and-comer Alex Carrington as a way to generate quarterback pressure without having to blitz a linebacker or cornerback needed in coverage.
The Bills mustered a respectable yet unspectacular 36 team sacks last year and 24 came from the four players expected to start along the defensive line in 2013.
Here's how they ranked as pass-rushers according to Pro Football Focus:
Finding imaginative ways to fluster opposing signal-callers was the Jets' trademark during Pettine's stint as the defensive coordinator, and his acumen in that area will be tested without Gilmore for the first month and a half of the season.
Inside linebackers Nigel Bradham and Kiko Alonso aren't established thumpers, yet they possesses the needed speed and athleticism to be used as effective blitzers if need be. On the outside, Jerry Hughes has been Buffalo's best defender during training camp and the preseason and amassed three sacks combined against the Minnesota Vikings and Washington Redskins this August.
Though used as a traditional strong-side linebacker in the Bengals' 4-3 defense last year, Manny Lawson is more potent rushing the passer, as PFF gave him a Top 10 pass-rushing grade his position in 2012.
Buffalo's linebacking corps won't initially intimidate offensive coordinators, that's for sure, but the front office astutely acquired players with pass-rushing specialities or raw potential in that area, guys ideally suited to be utilized in Pettine's blitz-predicated system this season and beyond.
In the secondary, 2008 first-round pick Leodis McKelvin, who was re-signed this offseason, will now be the No. 1 cornerback. He's been a major disappointment based on when he was drafted but was actually given a +3.8 grade by PFF in 2012, only +.4 of which came in coverage. The rest of Buffalo's defensive backfield is unproven:
- Crezdon Butler - 2010 fifth-round pick of the Pittsburgh Steelers. Bills are his fourth team. No career interceptions
- Ron Brooks - 2012 fourth-round pick of the Bills. He appeared in nine games for Buffalo as a rookie. Has 12 career tackles and four pass breakups.
- Justin Rogers - 2011 seventh-round pick of the Bills. Has played in 29 games. Fourth-lowest rated cornerback coverage grade by PFF in 2012.
- Nickell Robey - Undrafted in 2013.
That rather uninspiring group behind Gilmore essentially proves that Pettine's ultra-aggressive scheme must act as a masking agent, at least until some of the younger corners acclimate to the speed and complexity of the NFL regular season.
Jairus Byrd may not be in his finest football shape, but his range in center field should give Pettine some creative liberty when designing ways to force opposing quarterbacks out of their comfort zones. Though Aaron Williams has struggled in coverage as a professional and will begin a new career at safety this season, he's shown ability as a hard-hitting run stopper.
Without Gilmore, Buffalo won't have its Revis, a man-to-man "island" cornerback who allows the blitzing flood gates to be opened.
Due to that, Mike Pettine will have to be more selective in dialing up added pressure, but he'll likely lean heavily on the front seven for sacks and to force hurried throws, both of which must happen often to keep the Bills defense afloat until Gilmore returns.