The term "starter" doesn't mean what it used to in the modern NFL, particularly on the defensive side of the ball, where run-defending specialists and pass rush virtuosos rotate in and out depending on down and distance.

Some superstars may only play about 75 percent of a given team's defensive stats as coaches look to lighten the load on any given player, and stepping in, you'll see a lesser-known role player needing to provide consistent, quality snaps. Teams need a base run defender, like Dan Williams of the Cardinals, that can provide ballast to a front line. They need that situational pass rusher, like Tyrunn Walker of the Lions, that can get after the quarterback when it's a clear passing situation. And who can forget players like Brandon Boykin, one of those nickel and slot cornerbacks essential for defending three- and four-receiver sets.

In other words, every team needs a few out-of-the-spotlight guys who do the dirty work, the specific roles defensive coordinators need to make their scheme successful. (Here's our look at the offensive role players from last week).

So, who are the league's best role players? Let's take a look at a few that may not be stars in this league, but play important roles for their team.

Defensive linemen

Sharrif Floyd, MIN; Dan Williams, OAK; Tyrone Crawford, DAL; Tyrunn Walker, DET; Ryan Davis, JAC; Jordan Hill, SEA

Third-year Vikings defensive tackle Sharrif Floyd played 52 percent of his team's defensive snaps in 14 games in 2014, as part of a high-quality defensive line rotation that included Linval Joseph, Everson Griffin, Brian Robison, Corey Wooten and Shamar Stephen. The 6'3, 311-pound Floyd may be destined for stardom, but to this point has been a solid performer and key cog for what looks like a promising defense going into next year. He stuffed the run with aplomb while also showing some value as a pass rusher, racking up 4.5 sacks, 20 quarterback hurries and five quarterback hits. He's reportedly cut a little bit of weight this offseason, down to under 300 pounds, and he's a versatile and athletic player that fills a key role for the Vikings.

Dan Williams moves from Arizona to Oakland this offseason and joins another promising defensive front rotation. Williams played in 39 percent of the Cardinals' defensive snaps in 2014 and while that number may jump up to over 50 percent this season, his stats are never going to jump out at you. The 6'2, 330-pound nose tackle is a prototypical "war daddy" in the middle of the defense, eating up blocks, holding his ground, and allowing his teammates around him to flow to the football.

The Cowboys defense performed quite a bit better than most people were expecting going into last season, and some of that success can be attributed to the play of Tyrone Crawford. Crawford came back from a torn Achilles in 2013 and after playing the first three weeks at the end spot, moved inside to defensive tackle and won the starting job there. He had three sacks, 29 quarterback pressures and 37 tackles in 15 games for Dallas while playing in 61 percent of their defensive snaps, and should be a big force for Rod Marinelli's crew in 2015.

Tyrunn Walker played 28 percent of New Orleans' defensive snaps -- definitely a reserve role -- but after signing in Detroit, could see that number go up quite a bit. Ndamukong Suh, Nick Fairley and C.J. Mosely are gone for the Lions and Walker, the rotational nickel-down defensive tackle that the Saints didn't feel they could keep, should play a key role, where his snaps will almost surely double. In limited chances last year, Walker had 2.5 sacks and 14 quarterback hurries (per Pro Football Focus), and he could be that player to step in to replace Fairley's role in the rotation.

Jacksonville got a surprise contributor last year in defensive lineman Ryan Davis, who in just 27 percent of the Jags' defensive snaps, racked up 6.5 sacks, five quarterback hits, 13 quarterback hurries and two forced fumbles. That's crazy per-snap productivity, and Jacksonville will need him to play that role and more next year after losing top pick Dante Fowler for the year.

In Seattle, the Seahawks got some impressive production out of defensive tackle Jordan Hill, who had 5.5 sacks, 10 quarterback hurries, five quarterback hits and an interception in just 36 percent of their defensive snaps. He hit injured reserve late in the season but the Seahawks will be expecting him to play that key nickel-down pass rushing under-tackle role again in 2015.

Edge players

Olivier Vernon, MIA; Aaron Lynch, SF; George Johnson, TB; Brandon Graham, PHI

Olivier Vernon will likely again find himself overshadowed this season playing next to superstars in Suh and Cameron Wake, but he'll be a key piece of that Dolphin pass rush. The fourth-year defensive end has picked up 21.5 sacks through three seasons and last year posted 6.5 to go with his 29 quarterback hurries, 12 quarterback hits and two forced fumbles. He's productive and reliable in run defense as well.

The Niners will surely see some changes implemented up front on defense this season as they replace Justin Smith, but outside linebacker Aaron Lynch should continue to see his role grow. The rookie played in 49 percent of San Francisco's snaps last season, notching six sacks, 27 quarterback hurries, eight quarterback hits and four passes defended. He showed that the Niners' decision to select him in the fifth round was no mistake, and depending on what happens with Ahmad Brooks going forward, we could see him playing a pretty big role opposite Aldon Smith in 2015.

George Johnson is a prototypical "role player," a guy that nearly retired before earning a tryout with Detroit last season, eventually making the team and playing in 47 percent of their defensive snaps. The rotational end had six sacks, 27 quarterback hurries, five quarterback hits, and because of his productivity, was signed to an offer sheet by the Bucs before eventually being traded to Tampa Bay. He reunites with Leslie Frazier, who coached him in Minnesota, and should play a key role for his new team in 2015.

Meanwhile in Philly, despite a four-year, $26 million deal, Brandon Graham remains a key role player, until he's not. The pass rusher accumulated 5.5 sacks, four forced fumbles, 39 quarterback hurries and eight quarterback hits while playing in just 43 percent of the Eagles' defensive snaps. That's making the most of your opportunities, and it earned him a nice payday. It may also have earned him some more snaps.

Off-the-ball linebackers

Thomas Davis, CAR; Nigel Bradham, BUF; K.J. Wright, SEA; Koa Misi, MIA; Daryl Smith, BAL

When it comes to the word "gritty," it's hard to find a player grittier than Carolina's Thomas Davis, who has overcome three ACL tears to continue to play at a high level in the NFL. He racked up 129 tackles in 2014 and while he's no rotational player, he does have to live in the shadow of Cam Newton and Luke Kuechly in Carolina. Regardless, he's a highly respected leader that exemplifies what out-of-the-spotlight role players should be.

Playing on a stacked defense, it's easy to get overlooked, and both Buffalo's Nigel Bradham and Seattle's K.J. Wright know how that goes. Bradham had a breakout year for the Bills last season after they lost Kiko Alonso, and the rangy and athletic linebacker racked up 104 tackles, two forced fumbles and a pick. He'll have a tough challenge in 2015 in transitioning to Rex Ryan's 3-4, but he should play a key role. One of the reasons that Ryan traded Alonso was because of Bradham's strong play last year. Meanwhile, in Seattle, overshadowed by the Legion of Boom, Michael Bennett, and Cliff Avril, K.J. Wright remains a stalwart piece of the puzzle. His length and instincts make him a three-down player that can fill in at every linebacker spot. That versatility and dependability earned him an extension late last year.

In Miami, Koa Misi made the move from the outside to the middle after the release of Phillip Wheeler and the trade of Dannell Ellerbe, and acquitted himself well there despite being banged up much of the season. He'll be a key role player there again in 2015, and playing behind Ndamukong Suh should open things up for him to rack up tackle numbers and potentially get involved in some pass rushing. He's a solid coverage linebacker that may not get tons of recognition, but his role will be important.

Baltimore's Daryl Smith is another good example of an underrated talent that doesn't get the attention he deserves because he plays on a star-studded defense. He's about to begin his 12th year in the league, and is one of the Ravens' leaders on defense after racking up 120+ tackles in each of the past two years. He's a strong all-around player that can both defend the run and cover in the passing game.

Safeties

George Iloka, CIN; Reshad Jones, MIA; Da'Norris Searcy, TEN

The Bengals boast one of the best defensive secondaries in football and they're just getting better with the development of George Iloka, who starts his fourth season in the league and third straight as the starter at strong safety. According to Pro Football Focus' tracking, Illoka gave up zero touchdowns in coverage while surrendering an 18.4 quarterback rating on throws to his opponent in coverage. He picked off three passes and deflected six while racking up 74 tackles.

Miami's Reshad Jones is another underrated player, and after missing the first four games of the season to suspension, played solidly both in the run game and in coverage for the Dolphins. He picked off three passes while breaking up four, and finished with 80 tackles on the year. He's poised to become more of a household name in 2015 if his play remains consistent.

Tennessee got a solid player in free agency in Da'Norris Searcy, and the former Buffalo Bill gave up zero touchdowns in coverage last year while surrendering an opposing quarterback rating of just 21.5, according to Pro Football Focus. The 26-year old quietly grabbed three interceptions and 65 tackles last season.

Cornerbacks

Corey Graham, BUF; Xavier Rhodes, MIN; Brandon Boykin, PHI

Corey Graham signed a four-year, $16 million deal with the Bills prior to last season and didn't disappoint. Per PFF's tracking, Graham gave up a 57.0 quarterback rating when targeted, defending 11 passes and picking off two while only giving up one touchdown in coverage. The 29-year old is a great example of one of these "gritty role players" because with the exit of Searcy in Buffalo, Graham may be making the move to safety in 2015. At best, he'll be a starter at that spot and provide the Bills immense value because of that, and at worst, he'll be a great depth and rotational player in Buffalo's secondary on the outside.

In Philly, Brandon Boykin is an interesting case, and his play has been statistically very strong from the slot, his main role with the defense. He limited opposing passers to a 77.2 quarterback rating when passing to his coverage man per PFF, deflecting nine passes and intercepting one without giving up a touchdown. However, as strong as he's been in the nickel role, his snaps are limited (42 percent of all defensive snaps) because he hasn't yet played outside. Whether that changes in 2015 remains to be seen and the Eagles may not even need that after signing Byron Maxwell and drafting Eric Rowe, but at worse, Boykin could be excellent potential depth on the outside if injuries occur.

Meanwhile, in Minnesota, Xavier Rhodes is developing into a very nice cornerback, and makes this list because he still doesn't have the star recognition of some of the league's top players at that position. He'll play a key role in a secondary that has taken some big strides in talent over the past year or two, and this past offseason, the Vikings signed Terence Newman and drafted Trae Waynes in the first round, meaning Rhodes could be just a piece of the pass-defense puzzle. The third-year corner defended 15 passes last year while giving up just two touchdowns, and he only missed three tackles in run support.

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Some of these players are bound to ascend into superstardom and some are late into their careers with already-established ceilings, but whatever the case, they'll all play key roles for their teams in 2015. No franchise can put together a team of stars -- the salary cap won't allow it -- so they all have to make due with these role players at many of the key positions. The key to building a winner is not just in acquiring the flashy Pro Bowlers, but in putting the talent around them to make it all work as a cohesive group. As they say, you're only as strong as your weakest link.