The Raiders and their fans would be forgiven if they took a wait-and-see approach on rookie linebacker Khalil Mack.

After all, it was only four years ago when linebacker Rolando McClain arrived with a lot of hype as the eighth pick out of Alabama, only to get cut after three seasons and classified as a massive bust.

However, everyone is all-in on Mack, convinced that he is the real deal, the kind of can’t-miss prospect that the Raiders whiffed upon in the first round eight times since 2003.

“I’ve seen a lot of defensive rookies come in over the years, but the difference with this guy is, he’s more polished,” veteran offensive lineman Khalif Barnes said. “He has all the tools of an elite pass rusher in this league.”

Mack joined the Raiders in mid-May as the No. 5 pick out of Buffalo. He hasn’t done anything in the three months since to make anyone question the Raiders first-round selection.

The next test for Mack is showing what he can do in a game. He gets his first crack Friday night, when the Raiders play the Minnesota Vikings in both teams’ exhibition opener.

Mack said he isn’t much into self promoting. He’s just eager to do what he does best, play football.

“We’ll be able to see Friday,” Mack said, when asked if he knows what kind of player he’s going to be in the NFL. “I can’t tell you what kind of player I am or what kind of player I’m going to be, but I can show you.”

When pressed on the issue, Mack said:

“There’s a lot of talking involved in this level of play. I’m not a talker. I’m all about action, man. I like to go out and play football and show you what I can do instead of telling you.”

For that, let’s listen to left offensive tackle Donald Penn, who oftentimes is assigned with blocking Mack in practice.

“From what I’ve seen so far, he’s going to be one of those guys that you talk about for a long time,” Penn said.

Penn said Mack has that rare combination of speed, strength, instincts and intellect. If Penn doesn’t do everything just right on a given play, he said, Mack will exploit the weakness “make me pay for it.”.

Moreover, Mack always wants to know what he did wrong on a particular play, Penn said. Or he wants to know why he beat Penn.

Mack beat Penn twice in a one-on-one blocking drill Wednesday, and he still was in Penn’s ear an hour after practice ended.

“He’s getting better and better every day,” Penn said. “He’s growing well as a player. I can’t wait to see him unleash it.”

There were those who questioned McClain’s ability to make the jump from college standout to NFL impact player.

Several of those came from within the Raiders organization. However, then-owner Al Davis sided with the contingent that endorsed McClain and selected McClain in the first round.

There aren’t many vocal critics of Mack as he prepares to play in an NFL game for the first time.

If anything, there’s a consensus that Mack is going to be a productive NFL player, at least, and maybe even a dominant one.

Coach Dennis Allen has compared Mack to Denver Broncos standout linebacker Von Miller. General manager Reggie McKenzie likened Mack’s talents to those of Green Bay Packers linebacker Clay Matthews, who McKenzie was around when Matthews joined the league.

— Tight end David Ausberry underwent a procedure on his knee Wednesday, as planned. Allen said he doesn’t know how long Ausberry will be out.

Second-year player Mychal Rivera and Ausberry are competing for the starting job. Rivera ascends to the top of the pecking order with Ausberry sidelined. Nick Kasa and Brian Leonhardt suddenly are competing for the primary backup spot.

Ausberry suffered a shoulder injury during training camp last season and missed the entire season.

— The Raiders signed linebacker Spencer Hadley and safety Larry Asante and waived linebacker Marshall McFadden and safety Shelton Johnson. Asante has played in 17 games in the NFL. Hadley is an undrafted rookie who originally signed with the Saints in May. McFadden was waived-injured with a sore hip. He reverts to the Raiders injured-reserve list if he isn’t claimed by another team during a 24-hour window from the time he got waived.

— Great moment at the end of practice Wednesday: Allen asked 8-year-old Charlie DeGrange to break the huddle. DeGrange is battling an inoperable brain tumor. He just started treatment last week. It doesn’t take much to brighten someone’s life. Let’s hope this is the first of countless bright days for Charlie.

— Linebacker Kaluka Maiava (hamstring), guard Lamar Mady (ankle) and cornerbacks Keith McGill (groin) and Neiko Thorpe (undisclosed) missed practice once again.

Cornerback DJ Hayden (foot), safety Usama Young (quadriceps) and guard Lucas Nix (knee) remain on the physically unable to perform list.

— Rivera turned in the play of the day, when he beat safety Charles Woodson with a double move and hauled in a well-thrown pass from Matt Schaub.

Rivera got to his feet, ran the rest of the way to the end zone and said, for those nearby to hear: “Touchdown.” Yes, indeed, Mychal, that was a touchdown.

— Allen said he wants to take a look at all of his healthy players Friday, especially the younger ones. The main things is: “At the end of this game, we want to have a better feel for where we are as a football team.”

Jerry McDonald will write an advance on the game with far more of what Allen had to say about playing time, what to expect and who is and isn’t expected to play.

— Miles Burris worked with the first-team defense again Wednesday. Sio Moore ran with the second-team.

As for a scouting report on both players and where they stand, here’s this tidbit from Allen:

“Both of them are good young players and both of them, they’re really kind of in the same spot,” Allen said. “Miles played and started played for us two years ago. Sio played for us last year and Miles was relegated to spot duty because of the injuries and never was fully healthy. But I think both of those guys are good football players. Miles is a tough, physical, hard-nosed player. Sio’s probably got a little more athleticism. But I think both of those guys are very capable starting linebackers in the NFL.”

— The stands were filled with hundreds of youngsters from youth football leagues around the Bay Area as guests of the Raiders.