GREEN BAY—It's a curious description, the one Ryan Pickett gave this week for what it's like to face Adrian Peterson.
"The whole game is like a headache," Pickett said.
The term carries multiple connotations for Pickett, the veteran run-stopper who has battled the Minnesota Vikings' star running back more than any of his fellow Green Bay Packers defensive linemen.
The headache is physical, because Peterson can dish out as much punishment as he absorbs. He never makes it easy on a tackler.
The headache is also mental, because Peterson forces the entire defensive front to remain as patient as the running back himself. Pickett called it "discipline."
"You have to be gap sound," he said. "You can't leave your gap to try to go make a play, because wherever the open gap is, he finds it."
Last but not least, the headache is constant, because no matter how well a defense has bottled up Peterson for a handful of carries, or a quarter or two, he's always capable of breaking a big one.
"You just have to play hard the whole time," Pickett said.
Peterson's arrival at Lambeau Field on Sunday will be a day of reckoning for the Packers' run defense. The unit hasn't faced a back anywhere near this caliber since Houston's Arian Foster seven weeks ago.
The Packers shut down Foster, who ranks second in the league to Peterson in rushing yards. Green Bay held the Texans' star to just 29 yards on 17 carries.
But the Packers are coming off their worst performance against the run since the opener against San Francisco. Last week, the Giants piled up 147 rushing yards, averaging 4.7 per carry. The tackling issues that were a big problem in 2011 but had been shored up through most of 2012 suddenly resurfaced.
The early departure of defensive end C.J. Wilson, who injured his knee against New York, didn't help, and the Packers will be without Wilson again this week.
"It's a horrible feeling knowing I won't be out there this Sunday to help the team, my defense, to stop this beast," Wilson said.
Wilson's absence will force the Packers to play a Peterson neophyte in Defensive Coordinator Dom Capers' base defense, which employs three down linemen. Two of them will be Pickett and B.J. Raji. The third will have to be either Jerel Worthy, Mike Daniels or Mike Neal. The first two are rookies, while Neal has never faced the Vikings.
With outside linebacker Dezman Moses starting again in place of the injured Clay Matthews, that's another rookie in the front seven who has never battled Peterson before.
"You ask your teammates about him and you study up a little extra," Moses said of the preparation required. "It's clear on film he's a tremendous back. He runs extra hard, he's physical, fast, all the things you want in a back.
"But at the same time, it's still football. You have to play your block, shed your block and make a tackle. It's as simple as that. You focus in and hone in on your techniques throughout the week so you can be sharp on Sunday."
Against a Capers-led Packers defense, Peterson's results in a half dozen meetings have been mixed. Twice he's had a big day, including a 175-yard effort in the first meeting last year. But twice the Packers have had the upper hand, holding him under 60 yards. The other two contests were basically a draw.
Adding to the intrigue Sunday is that Peterson is in the midst of a truly special, if not historic, season. Just 11 months removed from an ACL injury, Peterson leads the NFL with 1,236 rushing yards through 11 games, 172 more than the second-place Foster. He has topped 100 yards in five straight games, averaging 147.4 per game over that span. His 5.8 yards per carry on the season is a full yard better than his career mark coming into 2012.
"Watching the run cut-ups (in film study), it was like a highlight reel," Pickett said. "He's averaging almost six yards a carry. That's unheard of."
Pickett tried to stop there, but the questions kept coming. The headache was already on its way.
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