The Raiders’ rebuilding job is almost complete. Even though they missed out on the playoffs, Oakland showed signs of competing for the first time in a number of years. GM Reggie McKenzie has built a hugely promising offense starring Derek Carr after a breakout year. The offensive line also played a significant part in his development, as did a rejuvenated Michael Crabtree and first-year wideout Amari Cooper.

The QB wasn’t the only breakout Raider last season. On the defensive side of the ball, Khalil Mack elevated his game to another level, while David Amerson looked reborn outside of Washington. Heading into the offseason, the Raiders’ roster appeared as if it had few weaknesses.

Below is a compilation of the Oakland Raiders’ 2016 offseason transactions, including free-agency moves and draft picks:

Offseason grade: A

Free agents/Trades

New Signings: CB Sean Smith, S Reggie Nelson, LB Bruce Irvin, OT/G Kelechi Osemele, LB Darren Bates

Re-signings: OT Donald Penn, OLB Aldon Smith, S Nate Allen, CB Neiko Thorpe, QB Matt McGloin, WR Andre Holmes, OT Matt McCants

Departures: S Charles Woodson (ret.), DE Justin Tuck (ret.), S Taylor Mays, OLB Lorenzo Alexander, WR Rod Streater, DE Benson Mayowa, WR Jeremy Ross, OT J’Marcus Webb, G Tony Bergstrom, OT Khalif Barnes, S Larry Asante, LB Curtis Lofton

The only pressing need for the Raiders was a corner opposite David Amerson. McKenzie has done more right than wrong in charge of Oakland’s personnel, but D.J. Hayden looks as if he will fall into the mistake category after ranking 105th amongst corners a year ago (104.1 QB rating allowed). Sean Smith is a dramatic upgrade, and an ideal fit in head coach Jack Del Rio’s single-high defense (73 percent of snaps in 2015). He didn’t come cheap, but corners who can shut down opposing receivers on an island in man have tremendous value in the modern NFL. Unsatisfied with one new starter in the secondary, the Raiders also signed Reggie Nelson, PFF's ninth-highest graded safety last season. Nelson is more of a short-term stopgap, filling the void left by Charles Woodson’s retirement perfectly. He allowed a QB rating of just 61.8, picking off eight passes for Cincinnati a year ago.

McKenzie found exceptional value signing productive veterans for below-market value. In-house free agent Donald Penn was retained, and at just $12 million ($6 million guaranteed) for two years. Penn is an excellent blindside protector. He ranked 11th overall among tackles in 2015, allowing just 32 combined pressures (12 knockdowns). In combination with Penn, Oakland brought in the top lineman on the market to complete the set up front; Kelechi Osemele is a mauling guard, and can take over at left tackle when Penn starts to decline. He could still stand to develop in pass-protection on the outside (Osemele allowed a hit and seven hurries in four starts at tackle), but certainly has the potential to man-up with edge rushers in the future.

Project offensive line (2015 season grades shown)

The Raiders’ spending spree did not stop at Smith and Osemele. Bruce Irvin was probably overpaid—he signed on for $9 million a year with $14.5 million guaranteed—but his versatility should make him an ideal fit in Del Rio’s varied front. Irvin will be allowed to attack more frequently, which should suit his skill-set. The 15th-highest-graded linebacker last season, Irvin is most effective rushing the passer and coming downhill against the run. While Aldon Smith is suspended and Mario Edwards Jr. recovers from injury, the former Seahawk will get every opportunity to prove he can collapse the pocket on a consistent basis.

2016 NFL draft

Round 1 (pick No. 14) Karl Joseph, S, WVU

Round 2 (pick No. 44) Jihad Ward, DE, Illinois

Round 3 (pick No. 75) Shilique Calhoun, DE, Michigan State

Round 4 (pick No. 100) (from Tennessee via Philadelphia) Connor Cook, QB, Michigan State

Round 5 (pick No. 143) (from Dallas) DeAndre Washington, RB, Texas Tech

Round 6 (pick No. 194) (from Indianapolis) Cory James, OLB, Colorado State

Round 7 (pick No. 234) Vadal Alexander, G, LSU

The Raiders’ draft was a mixed bag. Karl Joseph may have been slightly overdrafted at 14th overall, but no other safety possessed his skillset in this class. The small sample size and injuries are the major concern. Joseph showed the range to cover sideline to sideline, he punished receivers over the middle, and he ran step-for-step with wideouts in man coverage. It was only four games, but Joseph flashed special potential in 2015.

More help was found for the defense in the second and third round, with the selections of Jihad Ward and Shilique Calhoun. Ward felt like a pick based more on potential than production, but he didn’t even test that well at the combine. He ranked as our 145th overall defensive tackle, generating just 26 combined pressures in 345 rushes. In contrast, Shilique Calhoun ranked second amongst defensive ends with a very strong pass-rush grade. He amassed 76 combined pressures (28 knockdowns), second-most amongst edge defenders. Calhoun represents an absolute steal in the third round.

The profession of backup QB has never been so lucrative, perhaps unsurprisingly, considering the impact of losing a starting signal-caller can have on a season. Connor Cook still makes too many bad decisions, but he is also capable of hitting any throw from any platform. The question is not of value—we had a third-round grade on Cook—but whether fourth-round picks should be spent on backup QBs.

RB DeAndre Washington and G Vadal Alexander can both provide depth. Running back is one of the few positions on a stacked Raiders' roster where a late-round pick has a chance to earn playing time. Washington broke 67 combined tackles in 2015 and made his fair-share of big plays.

Finally, undersized pass-rusher Cory James can make an impact on special teams while he tries to transition to a linebacker role in Oakland.

Conclusion

The Raiders added probably five starters in free agency and the draft who will make an instant impact. Sean Smith, Reggie Nelson, and Karl Joseph could take the secondary from good to excellent. Bruce Irvin and Shilique Calhoun should ensure that fresh edge rushers consistently disrupt opposing quarterbacks. Retaining Donald Penn and signing Kelechi Osemele could transform the Raiders’ front five into the top unit in the league. If their younger players added in previous years can also take the next step, then Oakland will be a frightening proposition in 2016.