ALAMEDA — Amari Cooper, as it turns out, really and truly had been waiting for Thursday night since third grade.

That’s when he started playing wide receiver, on his first youth league team.

“I didn’t choose it,” Cooper said Thursday night after being picked by the Raiders in the first round of the NFL draft. “I wanted to play running back. Because when you’re young, all teams really do is run the ball. But we had two great running backs. One was the coach’s son. The other one was really good. But they knew I was a great athlete, too. And they used me at wide receiver.”

Maybe they’d also been watching scouting film. Cooper had been running pass routes in his Florida back yard since kindergarten.

“It was like when I was 5 or 6, before organized football,” Cooper said. “Me and my friends would just play against each other. We had to find ways to get open. I was already running routes, just finding ways to get open … When my coaches tried to teach me how to run a route, I was already good at it because I had been doing it already … I just didn’t know what the routes were called.”

Hey, they say Mozart was composing symphonies at age 5. Why is it so hard to believe that before other kids could cross the street, Cooper was refining his crossing routes?

All the Raiders know is, from the way Cooper played at Alabama while catching 31 touchdown passes, he was as “polished” a nonprofessional receiver as general manager Reggie McKenzie has seen. That was the word McKenzie and new coach Jack Del Rio kept using to describe Cooper. He is polished. Quick, fast and polished. He looks like someone who has played receiver all his life.

“His skill set, he can run a route,” McKenzie said. “It seems like he can do that with his eyes closed.”

Yet the Raiders, we have learned, do not plan to use him that way. They expect to have him run routes with his eyes open.

Fans will expect even more. They always do. And all they expect of Cooper is that he takes the Raiders to their next Super Bowl and save the franchise for Oakland while delivering free gourmet pizza and craft beer to every Raider fan in the 510 area code for the next 10 years.

You think that’s expecting too much?

“The expectation should be high for a young man that comes in that is selected that high in the draft,” said Del Rio, Cooper’s future coach. “But he’ll need to prove it on the field and earn it.”

Del Rio, meanwhile, sent a message himself with the pick, as did McKenzie. The Raiders had other options when their turn came up at No. 4. They passed on USC defensive lineman Leonard Williams, thought to be the best pure talent in the draft. Instead, the Raiders wanted offense.

This sent a message that they value Derek Carr, their young quarterback, enough to give him the best draft-day toy any quarterback in the league will receive.

And it sent a message that the new Del Rio administration will not be obsessively fixated on defense, despite the head coach’s background as an NFL linebacker and an assistant largely on that side of the ball.

It also sent a message that they have put behind them any fears of taking another No. 1 chance on a wide receiver after the failed experiment that was the Raiders’ last first-round selection at that position, Darius Heyward-Bey, in 2009. Heyward was not quite a full-fledged bust. But he created many non-fond memories of many dropped passes before leaving the premises in 2013.

Cooper has also received criticism for dropping passes, though most scouts who’ve examined the video believe they have been the result of him looking downfield too soon before seeing the ball into his hands. Cooper says he needs to work on improving “details” of his game and presumably that is one.

The only other unintended downside to his selection? The Raiders signed former 49ers receiver Michael Crabtree to a free-agent contract a few weeks ago that contains a lot of incentives for numbers of catches and yards. For instance, if he catches 70 passes or reaches 900 receiving yards, Crabtree gets $400,000. If Crabtree catches 100 balls, he gets $1.4 million. With Cooper on the roster, Crabtree’s odds of reaching those numbers greatly diminish. Del Rio will need to watch how that plays out in the wide receivers room.

For now, the coach is eager to see how his new route-runner looks in a Raiders uniform and not eager to compare Cooper to anyone in a current NFL uniform, although Reggie Wayne of the Colts has been mentioned along those lines. Del Rio just wants Cooper to be Cooper.

Read Mark Purdy’s blog at blogs.mercurynews.com/purdy. Contact him at mpurdy@mercurynews.com. Follow him on Twitter at twitter.com/MercPurdy.