Oakland Raiders' 2018 free agency: Rashaan Melvin fills a need at corner

A breakdown of the Oakland Raiders' 2018 free-agent signings.

Rashaan Melvin, CB

The Oakland Raiders have reached an agreement to sign cornerback Rashaan Melvin, who played the last two seasons for the Indianapolis Colts. Here’s a closer look at the pending signing:

Grade: B. The Raiders’ eighth announced free-agent signing was the third on the defensive side of the ball, and Oakland’s first at cornerback, a real and specific need.

What it means: While Melvin sees himself as being ready to assume the mantle of a No. 1 cornerback, the Raiders likely see him playing on the left side, with last year’s first-round draft pick, Gareon Conley, starting on the right. Of course, that’s contingent upon Conley being fully healed from his shin injury, which limited him to two games as a rookie. Melvin, meanwhile, went from being the Colts’ projected No. 3 corner last season to replacing the injured Vontae Davis, shadowing opponents’ top receivers, until Melvin suffered a season-ending hand injury in Week 12. Melvin is a relatively big corner, at 6-foot-2, 193 pounds, so you could assume Oakland would have him shadow the bigger wideouts, too.

What’s the risk: Sure, Melvin had a career-best three interceptions last season, along with 13 passes defensed, but they were the first three picks of his four-year career. And he has played at least 10 games in a season only twice in his career, so he has yet to show much staying power. Raiders general manager Reggie McKenzie has not had much success in either signing or drafting cornerbacks who succeed in Oakland, from Ron Bartell to Shawntae Spencer to DJ Hayden to Mike Jenkins to Tracy Porter to Tarell Brown to Brandian Ross to Carlos Rogers to David Amerson to Sean Smith. Is Melvin the antidote to what ails McKenzie’s eye for a solid cornerback with staying power?

Tahir Whitehead, LB

The Oakland Raiders have signed linebacker Tahir Whitehead, who played the last six seasons for the Detroit Lions. Here’s a closer look at the signing:

Grade: B-minus. This was the Raiders’ second straight announced free-agent signing on defense, and at a specific need.

What it means: Oakland has yet to re-sign NaVorro Bowman, and if he goes elsewhere, Whitehead has the experience to play in the middle. Whitehead, 27, is versatile as he has played both inside and outside, where he moved last season and had a sack, four fumble recoveries and an interception in starting all 16 games for the Lions. He is a tackling machine with 242 tackles, 177 solo, the past two years, and the Raiders could use some sure hands in that department in the defense’s second level, especially if Bruce Irvin sees more time with his hand in the dirt as an edge rusher, as Jon Gruden wants. Otherwise, how about a 4-3 scheme with Bowman in the middle, Irvin on the strong side and Whitehead on the weak side?

What’s the risk: As with the signing of safety Marcus Gilchrist to boost the secondary, none, really. That is, unless the Raiders let Bowman walk, insert Whitehead as the middle linebacker and he has lost a step or two and has trouble catching up with defensive coordinator Paul Guenther’s terminology and strategy. His 110 tackles, 17th in the NFL, came from the outside, so there might be another learning curve if there is more than see-ball, get-ball involved on a new team. Whitehead is, like Gilchrist, a nice complementary part to the defense, rather than a centerpiece, and the Raiders would be wise to surround him with players who would allow him to succeed.

Marcus Gilchrist, S

The Oakland Raiders signed defensive back Marcus Gilchrist, who played last season for the Houston Texans. Here’s a closer look at the signing:

Grade: C-plus. Finally, the Raiders addressed defense with their fifth announced free-agent signing of the day and attacked the much-maligned secondary. So that’s something, right?

What it means: The Raiders still have precious little experience at cornerback and perhaps even less at safety. Gilchrist, a second-round draft pick of the Chargers in 2011, brings a certain veteran stewardship to Oakland. He has played for the Chargers, New York Jets and Texans, recording 11 interceptions, 32 passes defensed and four sacks in 107 career games, including 82 starts. A versatile defensive back, he played 100-plus snaps at free safety, strong safety, slot corner and linebacker for the Texans last season, per Pro Football Focus, and he should team well with Karl Joseph in the back of the Raiders' reimagined defense. Gilchrist had an interception, a forced fumble and six passes defensed in 16 games, 13 starts, last season.

What’s the risk: None, really, unless the Raiders deem their work done in the secondary in free agency. Because while Gilchrist, 29, is a nice veteran pickup for the defensive backfield, he is a complementary piece, not a centerpiece. Besides, while he did have a solid year in Houston after joining the team in training camp, he did tear his patellar tendon in Week 14 of the 2016 season and had major knee surgery that December. And at 5-foot-10, 198 pounds, he is essentially the same size as Joseph, meaning they are not all that physically intimidating a safety unit.

Jordy Nelson, WR

The Raiders signed receiver Jordy Nelson, who played the past 10 years for the Green Bay Packers. Here’s a closer look at the signing:

Grade: B. No, Nelson cannot play cornerback or rush the quarterback -- two things Oakland needs more at the moment -- but he does bring a level of championship experience to the Raiders' receiving corps, which it could also use. Nelson has authored three seasons with at least 1,250 receiving yards and at least 13 touchdown catches, in 2011, 2014 and 2016. Only Hall of Famers Jerry Rice (six), Randy Moss (five) and Terrell Owens (four) have had more such seasons in NFL history.

What it means: Nelson, the erstwhile "White Lightning," likely assumes the role of possession receiver for Raiders QB Derek Carr, with Amari Cooper retaining his standing as the big-play pass-catcher. That made Michael Crabtree expendable; he was released before Nelson signed, saving the Raiders more than $7.68 million in salary-cap room for 2018. “Big body, long speed receiver who can help stretch the field,” former Raiders defensive back Charles Woodson told me in a text of Nelson, a former teammate with the Packers. “Does great job uncovering when qb breaks the pocket. Great teammate.” Nelson reunites with Raiders WR coach Edgar Bennett, who was both his position coach and offensive coordinator in Green Bay.

What’s the risk: Nelson turns 33 on May 31 and is coming off a 53-catch, 482-receiving yard, six-TD season, his lowest such marks since 2012, 2009 and 2010, respectively. He missed the entire 2015 season with a right-knee injury that he suffered in the preseason but flourished in his 2016 return, leading the NFL with 14 touchdown catches. His yards-per-catch average fell from 13.0 in 2016 to 9.1 in 2017. Then again, he had Aaron Rodgers as his quarterback for just seven games.

Doug Martin, RB

The Raiders have agreed to terms with running back Doug Martin, who played the past six years for the Tampa Bay Buccaneers. Here’s a closer look at the impending signing:

Grade: C. The 29-year-old Martin, also known as the Muscle Hamster because of his relatively diminutive size at 5-foot-9 and 223 pounds, has been a force before at running back in the NFL -- though not since 2015.

What it means: With Marshawn Lynch and Martin, Jon Gruden is trying to replicate the "Thunder and Lightning" running back duo of Tyrone Wheatley and Napoleon Kaufman from his first stint with the Raiders. Unless Lynch, due a $1 million roster bonus on Sunday, is out and Martin is the Raiders’ new bell cow back, along with mighty mites DeAndre Washington and Jalen Richard. Either way, it’s a curious signing considering the guy has averaged 2.19 yards per carry over the past two seasons and served a four-game suspension for violating the league's policy on performance-enhancing substances in 2016.

What’s the risk: Martin is a two-time Pro Bowler and may very well be reinvigorated by a return to his Northern California roots. But, again, he averaged 2.19 yards the past two seasons. He was benched in favor of Peyton Barber for the final three games last season. He was a healthy scratch in Week 15 for violating a team rule. And there’s that whole suspension thing. Still, with high risk comes high reward, right? Maybe the Raiders still imagine him being the guy that shredded them for 251 rushing yards and four TDs as a rookie in 2012.