ALAMEDA — The Raiders were fired up entering this season about their bookend pass rushers in Khalil Mack and Bruce Irvin.

Five games in, one of the biggest surprises might be that fourth-year defensive tackle Stacy McGee is the team’s leader with 2 ½ sacks. This for a player with just a half-sack over the first 42 games of his NFL career.

McGee had a career game in Sunday’s win over the San Diego Chargers, twice getting a piece of quarterback Philip Rivers. He had a strip sack against Rivers on the first play of the second half, although the Chargers recovered, and also split a sack with Dan Williams. He was credited with a second forced fumble when Melvin Gordon coughed one up.

“Stacy has done some good things for us,” Raiders coach Jack Del Rio said. “He’s flashed some rushes and been really close on a couple this year, so it was nice to see him finish on the two.”

Del Rio compared McGee’s move on one of his sacks to the “hump” move that Hall of Fame defensive end Reggie White used to abuse offensive tackles and quarterbacks over the years.

“That’s something I’ve been working on,” McGee said. “Antonio Smith was here a couple years ago and he showed us how to do the hump move. I guess it took a couple years to really figure out and get it done.”

McGee, a sixth-round pick from 2016, said he’s gradually gotten bigger and stronger and the 6-foot-3, 310-pounder notices the difference.

“On the field and in the weight room, I can definitely tell the difference of being able to lift more weights and move people around a lot better,” McGee.

The timing is good for McGee, who will be an unrestricted free agent this offseason as his four-year rookie contract expires.

The success on the field — he’s started all five games and has been the top pass rush threat on the interior line — is a result of a more dedicated player.

“I just put in a lot of work in the offseason to get better, a lot more work than normal, so it’s starting to pay off,” McGee said.

What inspired that extra work?

“My daughter,” McGee said of 1-year-old Gemma Jewel. “Everybody’s mindset is different but from a personal standpoint, it’s just wanting to give my daughter things that I never had growing up.”