NAPA, Calif. (AP) Despite being a top five draft pick, a heralded rookie and a selection on the NFL's top 100 players list, Oakland Raiders linebacker Khalil Mack is far from satisfied heading into his second pro season.

That attitude is fueled by the rejection he faced coming out of high school when he got only one scholarship offer to Buffalo rather than the opportunity to play at a higher-profile school.

It helped Mack pass all those five-star recruits to become the second defensive player drafted in 2014 and become one of the top outside linebackers - not just rookies - in the league last season.

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''I had a lot of space between Buffalo and those elite conferences, so I had to do a lot of work in order to get to that level, in my mind,'' he said. ''I'm still the same way. I feel like it's a lot of people on this level that are still great, but there's still a gap, so I'm trying to close it every day.''

That work ethic has been evident all offseason as Mack has impressed a new coaching staff that had seen him from the other side of the field and on film bit not up close.

So far, only one thing has been missing for Mack, and the Raiders believe that will change this season. Mack had just four sacks as he was unable to turn all that pressure into big plays.

''Everybody is saying how good he is and he got four sacks,'' new defensive coordinator Ken Norton Jr. said. ''I thought to myself, `How many great players have four sacks?' You have to get in double digits. So he has a lot of growth to make. If they're thinking he's this good and he's done so little, imagine when he actually does what he's supposed to do.''

In order to get to the quarterback more often, Mack added some extra pounds of muscle to allow him to use power as well as speed to beat NFL tackles.

Mack also could get more time as a defensive end this season under the new coaching staff after having a close to even split last season as a stand-up linebacker and a rush end with his hand on the ground.

''He's pretty doggone good getting after the quarterback,'' general manager Reggie McKenzie said. ''He's just really good going forward and it's an opportunity really to do a lot of things with him. They're going to use Khalil all kinds of ways and that's the way it should be. He's a dominant defensive player, so let him do what he does best and move him around.''

Mack hopes the added strength will help him deal with the longer NFL season and deliver the sacks that he was close to getting a year ago.

''It was a little frustrating,'' he said. ''Even then, I had talks with Justin Tuck. He let me know everybody gets lucky. It's not all just because of technique and being fundamentally sound. Everybody gets lucky and you have to know how teams are scheming against you.''

While many outside linebackers make their names by sacking the quarterback, Mack has been at his best against the run where he fights off blocks to make plays in the backfield every week. Mack was second in the NFL to Houston's J.J. Watt with 11 1/2 tackles at or behind the line against the run, according to STATS.

Mack is no slouch rushing the passer despite seeing more than his share of double-teams. In addition to his four sacks, he was tied for sixth among all linebackers with 51 quarterback pressures. Mack ranked third in quarterback pressures among linebackers over the last 11 weeks.

''Khalil is special,'' Norton said. ''There are a lot of players that might be similar. But he's in a class of his own. Bruce Irvin in Seattle was similar. But, at the same time, Khalil is built. He's athletic. He's smart. And he's relentless. ... He's amazing.''

Mack has earned comparisons with many of the top pass rushers in the league with former coach Dennis Allen likening him to Von Miller as soon as he was drafted.

Quarterback Derek Carr said Mack was similar to Kansas City's Justin Houston and Tamba Hali and Denver's DeMarcus Ware as well.

''I'm trying to go out there and be the best player I can be,'' Mack said. ''My name is Khalil. I want to be the best Khalil. Whatever he says about me, I appreciate it but I still have a long way to go.''

NOTES: WR Rod Streater and RB Trent Richardson remain on the non-football illness list. ... DT Stacy McGee is still on the physically unable to perform list. ... RB Roy Helu Jr. and TE Clive Walford are also sidelined.

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