Free-agent primer: Defensive tackles

Suh is the best DT available, but it's the guys underneath him on that talent line who provide a great deal of intrigue.

Defensive fronts are more creative and varied than ever in the NFL, and that makes the value of a truly great defensive tackle higher than ever. With all those different schemes and pre-snap movements, having a player who can hold things down in the middle is of paramount importance. And this season, Ndamukong Suh—the most talented and coveted free agent of them all—happens to play defensive tackle. Suh's new deal is a relative no-brainer—he'll probably get a deal comparable to J.J. Watt's six-year, $100 million contract with about $50 million guaranteed when all is said and done—but it's the guys underneath him on that talent line who provide a great deal of intrigue.

More 2015 free-agent primers: Running backs | Wide receivers|Edge-rushers

Overrated players

• B.J. Raji

Raji was once an elite 3-4 interior defender, but he was trending down a bit even before the biceps injury that cost him the entire 2014 season. In 2013, he amassed no sacks, three quarterback hits and 10 hurries, all downturns from seasons before. That would have been O.K. had he stepped up as a run-stopper, but he was inconsistent in that role as well. The Packers may re-sign Raji as part of their mission to improve a defense with a lot of holes, but they'll have to understand what he is and isn't at this point in his career.

[daily_cut.nfl]• Darnell Dockett

According to reports, the entire NFC West is interested in Dockett's services. The Cardinals, who have benefited from his services since 2004, have been joined by the 49ers, Rams and Seahawks in the derby for his services. Like Raji, Dockett missed the entire 2014 season due to injury (a torn ACL in his case), and the Cards released him in late February after he refused to take a pay cut. Dockett will be 34 in May, and though he can still be a fairly disruptive presence in the right system, he may also have to accept the fact that he's a rotational player at this point in his career.

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Underrated players

• C.J. Mosley

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It was an interesting season for the veteran, who replaced the injured Nick Fairley with aplomb after he had been suspended by the team for two weeks for a marijuana offense. Mosley is a bit-part player at this point in his career, but for any team looking to up their rotational impact in a 4-3 system, he might just fit the bill.

• Stephen Paea

The Bears' defense was one of the worst in modern NFL history against the run in 2014, but don't blame Paea for that -- he played through injuries in his contract year, showing the strength and competitiveness that had the Bears picking him in the second round of the 2011 draft. Paea, in fact, has become one of the better run-stopping tackles in the league, and he'll show that on a defense with a competent defensive coordinator. The mush-rush Chicago put up in 2014 wasn't his fault at all. Add in the six sacks, 11 hits and 31 hurries in that mess of a defensive line, and ask yourself: What kind of impact could Paea have in a better system?

• Dan Williams

The 6'2'', 327-pound Williams should be on the list for any team looking to bolster their run defense, especially those teams who play a 3-4 base defense with hybrid aspects. Williams had a few hits and hurries last season, but his primary attribute is the ability to sop up double teams and blast through to create negative plays in the backfield. That won't get him a top-level deal, but it will make him a key part of some team's roster.

Injured player to watch

• Nick Fairley

Given checkered past, is Ndamukong Suh worth the risk? No doubt about it

When he's healthy, in shape and staying out of trouble, Fairley is a rare player. Sadly, getting to that trio of circumstances isn't as easy as it should be. Fairley's weight fluctuations and off-field incidents make him a risky proposition, and the knee injury that cost him the second half of the 2014 season will have teams wondering if he's damaged goods at this point. Fairley is a dominant player at certain times, but there's nothing worse than an inconsistent player whose potential greatness forces you to break the bank, and that's what he looks like at this point.

Veteran to watch

•  Kevin Williams

In Seattle's over and under fronts through the 2014 season, Williams not only played his usual three-tech role, but slipped inside to nose tackle when Seattle's depth at the position plummeted due to injury. Williams fell just short of the goal set when he signed a one-year deal with the Seahawks -- win a Lombardi Trophy -- but he showed that not only does he still have something left to offer, he can do it in different positions. Who says you can't teach an old dog new tricks?

Biggest wild-card

•  Vince Wilfork's future in New England

The 33-year-old Wilfork has been one of the greatest players of the Bill Belichick era in New England, but his future tenure in Foxboro may come down to finances. Wilfork has a $4 million roster bonus that comes due on March 10, and his total cap hit for the 2015 season is $8,933,333. That's a lot for a team that's currently about $12 million over the cap, and the Pats could offset more than $8 million if they cut him. Though he came back like a champ from the Achilles injury that limited him to four games in 2013, Wilfork may have to take a financial hit in the short term if he wants to prove, as he's recently said, that he has a lot of football left.