The 10th overall pick in 2012 is arguably the AFC East's best cornerback entering this season, and is uncontested at the top of the depth chart in Buffalo.
But who will line up across from Gilmore, as the team's other starting cornerback?
The Bills have invested high draft picks at the position, including a first-round pick in 2008 (Leodis McKelvin) and a second-round pick in 2011 (Aaron Williams). At this point, McKelvin remains in the hunt for the job, while Williams is settling into the free safety spot left vacant by the absence of a franchise-tagged Jairus Byrd.
While it's always possible that Williams could slide back to cornerback once Byrd returns, the Bills had Justin Rogers as their top cornerback across from Gilmore to begin training camp Sunday.
Here's a look at the candidates for No. 2:
Rogers -- A seventh-round pick in 2011, Rogers has started one game in each of his first two seasons. In 2012, he played in 49 percent of defensive snaps, according to Football Outsiders, while also providing a presence on special teams (38 percent of snaps). The 25-year old who played at Division 1 FCS contender Richmond appears to be the frontrunner for the job. At 5-foot-11, 181 pounds, he has sufficient size for an NFL cornerback.
T.J. Heath -- Entering the league in 2011 as an undrafted free agent with the Jacksonville Jaguars, Heath spent most of last season on the Bills' practice squad. He didn't appear in a game for Buffalo, and has not started an NFL contest. When Rogers sat out team drills for unknown reasons on Tuesday, it was Heath who stepped in with the first team. The 25-year old Jacksonville State product has good size at 6-feet, 188 pounds, but appeared thin through his midsection during practice Tuesday. His ability to press receivers off the line will be something to watch during live game action.
McKelvin -- The most experienced player in Buffalo's secondary, McKelvin has started 33 games over his career with the Bills. His contributions on defense have tailed off in recent seasons, though, and he played in just 32 percent of defensive snaps last season. McKelvin is a threat on special teams, returning two punts last season for touchdowns, and at 5-10 and 185 pounds is slightly undersized for his position. McKelvin missed OTAs and minicamp this offseason recovering from a groin injury that ended his 2012 season, and head coach Doug Marrone hinted Tuesday that McKelvin is still getting back up to speed, which could explain his position on the depth chart at this point.
Whoever earns the starting job, it's important to remember one thing: proven pass-catchers in the AFC East are relatively scarce.
Here's a breakdown of which receivers the Bills' No. 2 cornerback will square off against for six of the team's 16 games this season:
Miami Dolphins -- If Gilmore matches up against speedy free-agent signing Mike Wallace, then the other cornerback will be tasked with defending Brian Hartline. He's coming off a career season with the Dolphins, and the biggest problem could be his size. At 6-foot-2, Hartline presents match-up problems for Rogers, Heath, or McKelvin. This will be the biggest challenge on the division slate.
New England Patriots -- The Patriots will likely use Danny Amendola in the slot, which could draw Gilmore into an inside role. The Patriots are still searching for answers on the outside. Whether it's veterans Michael Jenkins or Kamar Aiken, or rookies Aaron Dobson, Josh Boyce, or Kenbrell Thompkins -- and yes, the competition in New England looks to be that wide open -- the problem in almost any case is still size, especially with Jenkins (6-foot-4) and Dobson (6-foot-3).
New York Jets -- The Jets' struggles at receiver from recent seasons look to carry over into 2013. Top target Santonio Holmes is injured, and the Jets need more out of 2012 second-round pick Stephen Hill. In any case, the No. 2 receiver in New York shouldn't be a major issue for whoever earns the starting role at cornerback in Buffalo.