Fernando Mendoza took every first-team snap at Raiders practice Wednesday. That part was new. The throws that have his teammates looking forward to his first NFL start Sunday? They’ve been seeing those for more than nine weeks.

“He was out there slinging it,” the Raiders tight end Brock Bowers said. “Nothing new, though. That’s what he’s done the whole time.”

There might not be a better explanation for how the Raiders got comfortable trading their starting quarterback to the Vikings on Tuesday, right smack in the middle of a season in which Cousins was playing about as well as all but 10 or 12 quarterbacks in the NFL. At 4-5, with eight games to play, the Raiders still had a playoff race to worry about.

And yet they just handed the offense to a 22-year-old about to make his first NFL start Sunday against the Seahawks.

From the outside, that’s a pretty good leap of faith. Inside the building, the Raiders had months of work to go on. And some of the people best qualified to explain what they saw spent a lot of that time on the receiving end of it.

“We’ve been seeing it all year. He’s been taking reps with us,” wide receiver Tre Tucker said. “He’s been doing everything.”

Every so often, a ball would come off Mendoza’s hand that reminded Tucker how the kid wound up in Las Vegas in the first place, by way of a Heisman Trophy, a national championship at Indiana and the first overall pick in the NFL draft.

“You just see a throw in practice and say, ‘Wow.’” Tucker said.

Tucker gets to see those throws behind the scenes. Come Sunday, a whole stadium full of fans who have spent the better part of nine weeks asking about Mendoza will finally get a look for themselves. Count Tucker among those a little more amped than usual to get to game day.

“For that to be out there this Sunday is going to be fun,” he said.

Left tackle Kolton Miller is usually too busy protecting Mendoza to see where the ball lands. He’s heard enough in the huddle, though, to know the rookie can get everybody’s attention.

“I know he seems kind of quirky,” Miller said. “But on the field, he commands the huddle. He speaks with volume.”

That carries some weight coming from the guy whose job it is to protect Mendoza’s blind side. So does the distinction Miller makes. Whatever anyone thinks of Mendoza’s mannerisms, the veteran left tackle has no trouble hearing him, and there’s no confusion about who’s running the offense.

How did Mendoza find his voice while Cousins was still doing most of the talking? Raiders coach Klint Kubiak would take you back to April, when Mendoza started preparing for the chance he’ll get Sunday against the Seahawks.

A first NFL start can make a young quarterback feel like everything is coming at him a million miles a minute. Kubiak figures all those weeks Mendoza spent preparing as if he’d be the primary voice in the huddle should turn the volume down a little.

“It shouldn’t be a whirlwind if he’s been preparing the right way each week,” Kubiak said. “At some point he knew he was going to get an opportunity, and so he’s been preparing that way since April.”

Sunday brings a part of the job nobody could duplicate for Mendoza while Cousins was here. If the Raiders go three-and-out on the opening series, it falls to him to get them going on the next one. Part of which requires Mendoza to understand quarterback brilliance sometimes comes down to just doing your part.

“We have such a great offensive staff, and we have such a great offense,” Mendoza said. “Whether it was leaders in the offensive line, leaders in the receiver room, leaders in the tight end room, or leaders in the running back room that I believe that they’re going to help me along the way to best execute my 1/11th, so we could all move forward and be efficient and effective as an offense.”

One of those guys is Bowers. Another is Tucker. Imagine what it would mean to Mendoza to get that first completion under his belt Sunday, to look up and see one of them on the other end of a throw he’s waited nine weeks to make.

You can already imagine what Bowers would say about it. Something along the lines of “been there, done that.”