Oakland Raiders general manager Reggie McKenzie spent years rectifying the personnel mistakes of previous regimes. He took over a team in salary cap crisis and patiently guided them through a transition period of frugality in free agency. The approach finally came to fruition last season, as the Raiders improved dramatically under new head coach Jack Del Rio to a 7-9 record.

With a stable core of talented players already in place, McKenzie obviously decided the time for patience was over, making several splash moves in free agency this offseason. Whether that decision to splurge on the open market proves a necessity in putting his team over the top, or a hasty alteration of an effective strategy, remains to be seen.

[More: Be sure to check out PFF’s ranking of all 32 NFL QB situations, offensive lines, running back units, receiving corps, secondaries, and defensive front-sevens. Catch up on all the team previews here.]

Carr a shining success at QB, after years of failure at the position

Quarterbacks: 11th in PFF's season preview rankings

The single biggest issue debilitating the Raiders’ playoff push has been an inability to find a quarterback. Years of searching resulted in nothing but disappointment. Derek Carr changed all that in a single season, improving significantly from his rookie year. He developed under pressure, boosting his adjusted completion percentage from 54.2 to 66.7 percent when facing the rush. The Raiders’ quarterback also hit at a much better rate on downfield throws, almost doubling his adjusted completion percentage on 20-plus yard passes (23.9 to 46.3). A revelation in his second year, Carr’s numbers could have been even gaudier had he not lost 375 yards on dropped passes (sixth-most in the league). We might see Oakland’s quarterbacks ranked much higher than 11th next season if Carr continues at this level of progression.

Raiders opt for a cheap, young backfield

Running backs: 24th

None of the Raiders’ running backs are household names. Although far from the most inspiring group, the unit is perfectly solid. Latavius Murray broke the 1,000-yard barrier, but required 266 carries to do so. Backups Taiwan Jones, Roy Helu and Jamize Olawale were only afforded 57 combined rushes. Fifth-round rookie DeAndre Washington might get some time in the rotation, but is unlikely to improve the backfield significantly as a rookie.

Starting WR duo possesses elite potential

Receiving corps: 18th

Amari Cooper made plenty of plays in his first season in Oakland, but also left a ton on the field. Assuming he is even slightly more sure-handed, he’ll likely improve to the status of impact starter. His 58.8 percent catch rate and four touchdowns on downfield receptions in 2015 certainly suggests that he is a big-play threat. On the opposite side, a new environment clearly got the best out of Michael Crabtree. He bounced back from a dreadful season in San Francisco with the second-best receiving grade of his career. Crabtree also managed to get within reach of his career-highs in touchdowns (nine) and broken tackles (17). Health, however, remains a serious concern. The depth behind the starting pair is at best unproven, and at worst alarming. 2015 third-round tight end Clive Walford is the only other legitimate receiving threat on the roster.

Free-agent signing completes a dominant offensive line

Offensive line: 2nd

Shattering the guard market is not such a concern when the player in question can also line up at tackle. Kelechi Osemele is better inside, where he can use his physicality to bully opponents, but he’s good enough on the perimeter to make kicking him outside a realistic option down the road. But for now, Osemele can be at his most natural position, following left tackle Donald Penn’s re-signing. The former Buccaneer graded 11th overall at the position a season ago, giving up just 31 combined hurries in 644 snaps. The remaining starters are all solid. Center Rodney Hudson ranked sixth overall, bettering his peers with just seven combined hurries conceded all year. Left guard Gabe Jackson and right tackle Austin Howard also ranked in the top 15 at their respective positions. Assuming the starting five all stay healthy, the continuity will undoubtedly help the unit improve even further.

The defensive front is stacked, too

Front seven: 5th

Khalil Mack is not considered on Von Miller’s level because he has yet to change games in front of a national audience, with a title on the line. While Miller has a Super Bowl ring and MVP trophy, Mack’s regular season was arguably better. He managed an astounding 82 combined pressures, adding a further 54 run stops. Both figures topped the league among edge defenders. Nose tackle Dan Williams is the next-best Oakland lineman. The former Cardinal elevated his run defense to another level in 2015, as well as recording a career-high 21 QB pressures. Supplementing the veterans are a group of underrated young players. Denico Autry, Mario Edwards Jr. and Justin Ellis were all effective a year ago, without being spectacular. It will be intriguing to see how free-agent pickup Bruce Irvin (formerly of Seattle) is used in Oakland, but he should be an instant upgrade to an off-the-ball linebacking corps that lacked talent a season ago. He will certainly need to play well if Ben Heeney (64.4 overall grade) and Malcolm Smith (58.6) do not improve significantly.

Secondary overhaul is likely to pay big dividends

Secondary: 9th

Oakland added three new starters who were highly productive last season. Former Chiefs cornerback turned Raiders free-agent signing Sean Smith’s size-speed combination is freakish. He’s able to eliminate the majority of receivers in press-man because of it. First-round pick Karl Joseph probably had the best senior season of all safeties in college last year, albeit he got on the field for only four games. Safety is one of the rare positions where players often improve with age, as instincts and experience are so important as the last line of defense. No player better illustrates that than Reggie Nelson, who recorded the second-best season grade of his career in 2015 (84.2 overall). If David Amerson can prove last season was no fluke (he went from our lowest-graded corner all the way up to 14th), the starting secondary will have no weaknesses. Nickelback TJ Carrie’s 2015 performances were concerning, especially because of his 14 missed tackles from 72 attempts, but the secondary’s outlook remains promising.