KANSAS CITY, Mo. – Dan Williams had options in free agency. The monstrous nose tackle considered several factors when choosing the Raiders, but edge rusher Khalil Mack was an attraction.

Mack was already known as a game-changer, though he certainly wasn’t the force he’s now become. He had just four sacks as a rookie, but the second-year pro leads the league with 15 heading into Sunday’s season finale at Kansas City. Williams saw this jump coming a long time ago.

“He’s part of the reason I came here,” Williams said. “I told Mack, ‘I’m expecting 20 sacks each year.’ He may be leading the league but he’s still five short. He need to get another five-piece this week.”

Williams said these things with a smile, but he could be serious about “another five-piece.” Mack has done that once already this season, when he dominated the Denver Broncos in Week 14 with five sacks and a safety.

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Odds of that happening again are extremely slim. Odds of him taking the sack title are not. Houston’s J.J. Watt is a half-sack behind heading into a contest against Jacksonville. Sunday’s performance will likely dictate who wins the award.

Don’t expect Mack to say he’s gunning for it or one more sack to match the franchise record. He only cares about wins. Mack admits he’ll check the box scores come Sunday night to see how it shakes out.

“You’ve got to especially now,” Mack said with a smile. “It’s pretty cool to see and kind of comparison…It will be cool to see after this week, but we’re only trying to get this win.”

Victories and heavy sack totals can work together, and he wouldn’t mind doing a bit of both in his last game.

“It would be pretty cool,” Mack said. “It’s a testament to hard work, team work along the defensive line, the whole defense and our offense, too. Put (quarterback Derek Carr) in there contributing, getting touchdowns and making the quarterback think about they have to do, so it’s just a testament to hard work all around.”

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A few sacks would be a bonus, but it’s not something Mack can actively seek. Pressing doesn't help, and he'll rely on what brought success all season. While the stat jump has been massive, it's hard to say anyone, including Williams or Mack, is surprised by it.

"Hard work pays off. God is good. That’s all you can attribute it to," Mack said. "You can say it’s surprising but, if you work hard enough, some of that stuff can feel like it’s supposed to happen."

Williams said Friday what the coaches have said all season. Mack hasn’t realized his full potential. The 25-year old still has technique to refine and learn that he can take over games up front. Those things will come with experience.

Mack has already made a real impression. He made the Pro Bowl despite finishing sixth in fan voting. Players and coaches helped him get in, knowing first hand how dominant he can be. Mack just stays focused on wins, and he says the Raiders don’t have enough. They wouldn’t have as many sans No. 52 creating havoc up front.

“Without Mack, some of the wins that we have, we probably wouldn’t have them,” Williams said. “He means a lot for the team. The things he does for us definitely helps the team win.”