Khalil Mack's replacement -- Tank Carradine takes the stage at least for a preseason game

Injuries and ineffectiveness have dulled the impact of former 49ers second-round pick Tank Carradine, but he's getting a shot in Oakland. AP Photo/Eric Risberg

OAKLAND, Calif. -- Much was expected of Cornellius "Tank" Carradine when the San Francisco 49ers used a second-round draft pick, No. 40 overall, on him in 2013.

More might be needed out of him now with the Oakland Raiders.

Such is Carradine's lot after he signed with Oakland as a free agent in March and has been thrust into a position at left defensive end held by Khalil Mack, whose holdout for a contract extension reached 15 days on Friday.

Fair? Hardly. Then again, you might say the football fates have been less than fair to Carradine since he entered the NFL. Injuries and ineffectiveness plagued him during his time with the Niners, limiting him to just 44 games, including eight starts, in five years.

"Time there kind of ran out," said Carradine, who has 5.5 career sacks. "I didn't have the success I wanted. I feel like I was in different schemes and didn't find the right scheme that actually fit me."

And when he finally found it last season, he missed eight games because of a high-ankle sprain.

To be fair, Carradine is not expected to step in and replicate Mack, who made NFL history in 2015 when he was named first-team All-Pro at two positions, outside linebacker and defensive end, and was the 2016 NFL defensive player of the year.

Mack, the No. 5 overall pick of the 2014 draft, has 40.5 career sacks with nine forced fumbles, four fumble recoveries and a pick-six.

"It feels good, you know," Carradine said of getting Mack's reps in training camp, while rotating inside on certain packages.

"... Whatever role they give me, I'm going to play the role and do the best to my ability to help the team win and help the younger guys. Can't wait for Khalil to come back. I'm excited to play with him, be out here with him and Bruce [Irvin] and be inside as well with the younger guys and Mario [Edwards] as well."

Despite the presence of Mack, Irvin and Edwards, the Raiders finished last in the NFL in sacks in 2016 with 25 and tied for 24th last season with 31.

Now, Carradine is not expected to be some sack-master in new defensive coordinator Paul Guenther's stunt-heavy 4-3 base defense, but he is expected to hold things down until Mack returns.

"Yeah, you know, he's healthy for the first time, too," Raiders coach Jon Gruden said. "Not only has he played multiple positions but had some injuries coming out of Florida State. Had a tough start to his career. But he's a high draft choice. I got a lot of respect for [former 49ers GM] Trent Baalke. This is a good football player.

"We like him as a six-technique particularly, head up on the tight end. Very hard-nose run defender with some pass-rush ability. He's done a nice job for us."

The Niners dabbled with the 6-foot-4, 270-pounder as both a pass-rushing defensive end and an inside run-stuffer. Nothing truly fit.

"Tank's a physical player in there," Guenther said. "Over the tight ends, tough to block for a tight end. He's picked it up. He's smart. He's understanding our defense. All the different blitzes and the coverages and fronts that we're running. He's been a real good surprise for us."

All-Pro left guard Kelechi Osemele said Carradine was "strong" and "he has a good bull rush."

Carradine is on his fifth head coach in six years -- Jim Harbaugh, Jim Tomsula, Chip Kelly, Kyle Shanahan and Gruden -- and, obviously, looking for some continuity.

"This is a good fit for me because, my last year with the 49ers was the same role that I'm having this year -- playing in base, third-down, rushing inside," Carradine said. "So, as they watch film and do all the years, I guess they pick up that, that's more me. Playing in base, stopping the run, be able to get the opportunity to rush inside, because I'm more of a long-armed power-rushing guy."

He's also part of an influx of new talent on the Raiders defensive line, along with rookies P.J. Hall, Arden Key and Maurice Hurst. In fact, Carradine said he was particularly impressed with Hurst, telling him, "You already know what to do, maybe you can help me out."

Carradine laughed.

"He probably learned that from Harbaugh," Carradine deadpanned, referencing Hurst playing for Harbaugh at Michigan.

Gruden, though, said starters would not get much, if any, run in tonight's exhibition opener against the Detroit Lions. They got plenty of work in specific situations in two days of joint practices this week.

Carradine, meanwhile, is eager to enter a season healthy and, well, be effective ... even if he has big shoes to fill with Mack watching from afar.

"Rush inside," Carradine said. "I'm excited to be given the opportunity to be able get down there, get on the guards, get some one-on-ones, and be able to get to the quarterback. That's something that I feel like the 49ers didn't really give me the opportunity to do.

"I've just got to show what I can do inside."