ALAMEDA — Thus concludes the most important offseason in the history of a storied franchise.

When coach Jon Gruden canceled Thursday’s final practice of the Raiders’ mandatory mimicamp, players went their separate ways until training camp convenes on July 26 at the Napa Valley Marriott.

The roster bears little resemblance to the one that left the field in a 35-3 loss to the Kansas City Chiefs last Dec. 30 to finish 4-12. A team that couldn’t move the ball consistently on offense and gave up a franchise record 467 points with just 13 sacks on defense has undergone the most dramatic and talked-about overhaul in the NFL.

Gruden and new general manager Mike Mayock, under authorization by owner Mark Davis, were on the attack from the outset. They brought in big-ticket veterans in their prime such as wide receiver Antonio Brown, wide receiver Tyrell Williams, right tackle Trent Brown and slot corner LaMarcus Joyner at a combined cost of more than $109 million in guaranteed money.

The draft, bolstered by last season’s trades of Khalil Mack and Amari Cooper, added three first-round draft picks that are expected to contribute immediately, plus other picks that could quickly be in the mix for playing time.

The Raiders stayed healthy throughout the offseason other than losing running back Isaiah Crowell to a torn Achilles’. They acted quickly, bringing back Doug Martin, who had a bounce-back year in 2018.

A look at the eight most significant developments of the Raiders’ offseason:

1. Hiring Mike Mayock

Much of what happened in terms of personnel is because of the out-of-the-box decision to bring in the longtime NFL Network draft expert to replace Reggie McKenzie. He and Gruden share a lot of beliefs, but it appears as though Mayock can counterbalance the coach’s impulsive nature and help steer him away from past-their-prime veterans in favor of youth and speed.

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The Antonio Brown deal, in particular, had Mayock written all over it. He was adamant about not giving up a draft pick this season in the first two rounds and ended up getting the most productive receiver in the NFL for third and a fifth.

The Raiders should be much better in 2019. They’d almost have to be, so there exists a possibility for an immediate payoff. In the longterm, Mayock also helped rebuild the scouting department with hires such as Jim Abrams (college scouting) and Dwayne Joseph (pro personnel). The Joseph hire, in particular, was looked at with envy in some NFL circles.

2. Trading for Antonio Brown

The biggest splash of the offseason was the Raiders’ acquisition of Brown, whose six-year run of production is on par with anything Jerry Rice did over a similar span.

Brown’s sometimes puzzling behavior isn’t everyone’s cup of tea. He wore out his welcome with the Pittsburgh Steelers. But Brown has four qualities Gruden loves. He produces on the practice field and meeting rooms. He produces on game day. He has an insatiable thirst to get better. He’s durable and always answers the call.

However it went down in Pittsburgh, Brown signing with the Raiders had a ripple effect. Along with the considerable dollars Davis was willing to invest, it made wearing silver and black an intriguing destination for the likes of Trent Brown, Williams and Joyner to come aboard as unrestricted free agents.

There will be some moments bordering on the bizarre, to be sure. But the worst of it will probably happen in Las Vegas. Brown shows every indication of proving himself as a Raider under Gruden in Year 1.

3. The draft haul

The pick of Clemson defensive end Clelin Ferrell at No. 4 overall wasn’t well-received by draft analysts and pundits, with the feeling he could have been had later. But the Raiders believe he is everything they want in an end who can pressure the pocket and stop the run. Plus, by all accounts Ferrell is off the charts in terms of leadership and character.

It doesn’t help he’ll be compared to Mack, a No. 5 pick in 2014. If Ferrell doesn’t produce in a big way (keep in mind Mack had just four sacks as a rookie) the Raiders will continue to get bashed for letting one of the top defensive talents in the league get away over a contract standoff.

Should Josh Jacobs blossom into a 1,200-yard runner and Johnathan Abrams as a force in the secondary, it would go a long way toward public perception being changed with regard to the trades of Mack and Cooper.

Second-round pick Trayvon Mullen, a cornerback, and Maxx Crosby, an edge rusher could also figure prominently sooner rather than later.

4. A schedule gut punch

The Raiders biggest impediment to going from 4-12 to .500 and beyond was provided by the NFL on April 18 with the release of the 2019 schedule. The Raiders already had the most difficult schedule in terms of the 2018 winning percentage of their opponents at .539.

Then came the news that after opening at home against Denver and Kansas City, with the Chiefs on Sept. 15, the Raiders won’t play at the Coliseum until Nov. 2. They play at Minnesota in Week 3, Indianapolis in Week 4, then travel from Indianapolis to London to face Mack and the Chicago Bears in Week 5.

Following a bye, the Raiders are at Green Bay and at Houston before coming back home to face the Detroit Lions in Week 9.

Through gritted teeth and a sarcastic smile, this is how Gruden assessed the 2019 lineup on draft day: “I think the league did a good job challenging us with our schedule — who we play and when we play.”

Considering the Chiefs are the opponent for Week 2, it’s hard to imagine a more important first game than the home date on Monday night against Denver. Lose, and the Raiders could be 2-5 or worse by the time they get back to the Coliseum and home fans who are expecting big things or else in what likely is their final year in Oakland.

5. Staying at the Coliseum

In a sense, you really can’t blame Davis for angrily checking out other options once the city of Oakland filed suit against his team over the move to Las Vegas.

But it was clear at the outset there were no other options. The 49ers weren’t throwing out a welcome mat at Levi’s Stadium, and Davis didn’t want it anyway. There was a silly dalliance with the Giants about playing at Oracle Park, but local politicians in San Francisco wanted no part of the Raiders. The 49ers objected, claiming territorial rights.

Staying in Oakland was the worst possible solution, except for all the others. The circus made all parties look bad — the Raiders, the 49ers, the Giants and the politicians. In the end, Davis did what was best for the team in 2019 in terms of continuity. Not that there were a lot of other possibilities. It’s not easy being a lame duck.

6. Derek Carr is still the quarterback

This is listed only because it was a running national storyline that Gruden was prepared to throw Carr overboard for the likes of Kyler Murray or Dwayne Haskins. He was likened to a poor poker player who couldn’t disguise his tell.

Quarterback Derek Carr is entrenched as the starter in 2019.It never made sense, though, given that Carr had grown in a difficult system and put up more than respectable numbers despite a dearth of surrounding talent and poor pass protection. Gruden has never entrusted a team to a rookie starter going into a season and this wasn’t the time to start all over.

And while speculation about the quarterback will be inevitable as long as Gruden is the coach — the only one who truly had his complete trust was Rich Gannon — Carr will be given every chance to lead the Raiders into Las Vegas in 2020. And deservedly so.

7. Chemistry issues

How could the Raiders go all-in on character in the draft and then bring in characters such as linebacker Vontaze Burfict and Richie Incognito?

Throwing the former Bengals linebacker and the notoriously volatile left guard in the locker room along with Antonio Brown has some wondering if the Raiders are fond of combining baking soda and vinegar. It makes for an interesting story, but both men are basically on “prove it” deals. And “prove it” doesn’t mean being part of the future in the years ahead, it means being on the 2019 roster at all.

They’ll both be given every opportunity to prove that 1) they can still play; and 2) they can conduct themselves in a team-first manner.

8. `Hard Knocks’ comes calling

Thirty NFL Films cameras will shoot reams upon reams of footage in Napa as the Raiders go under the HBO microscope for the popular five-week series.

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How will Gruden act? How will the players respond? And even though the Raiders have a lot of control as to what goes into the series, if there’s a training camp hiccup, it will be soap opera fodder for all the country to see.

The Raiders will never be more scrutinized than they are in this training camp heading in to what should be the final year in Oakland.

And it was one of the busiest off-seasons in memory that set the stage.