GREEN BAY – Uncommon opponents are always a challenge, and the 2018 Buffalo Bills are about as uncommon as it gets for the Packers.

Head Coach Mike McCarthy pointed out on Wednesday that not only have the Packers not played the Bills for four years – the standard rotation of NFC-AFC matchups – but also the Bills have only two players still on the team from the 2014 meeting.

The Packers still have roughly 20 percent of their team compared to four years ago.

"We don't know them, they don't know us," McCarthy said prior to Wednesday's practice. "It's important to get in tune with the uncommon matchups we're going to be involved in. That'll be the biggest challenge through the week and come Sunday.

"But at the end of the day, we're going to spend more time on ourselves. We have a number of things to improve on and get ready for."

One of those is Buffalo's defensive pass rush. On onslaught of pressure on Minnesota QB Kirk Cousins led to turnovers and helped stake the Bills to a big early lead last Sunday in Minneapolis that led to a 27-6 victory almost no one saw coming.

Buffalo had been 0-2, but as rookie QB Josh Allen continues to settle in, the Bills are expecting to look more and more like the team that broke the franchise's long playoff drought a season ago.

"It shows our league, the competitiveness of our league," McCarthy said of Buffalo's huge road win at Minnesota. "When you get into the third, fourth, fifth game, things start to clear up as far as what people are trying to do. Their pressure on defense, especially early, in normal down-and-distance, was different (vs. the Vikings) and they got production out of that, too."

On the injury front for the Packers, cornerback Kevin King (groin) will work in the rehab group on Wednesday as new addition Bashaud Breeland hits the practice field in Green Bay for the first time. Outside linebacker Nick Perry is in the concussion protocol.

Quarterback Aaron Rodgers (knee) also will be in the rehab group, and McCarthy said he remains "day to day" as far as his practice availability.

Not having Rodgers practicing regularly is obviously not ideal for the Packers, and McCarthy stressed that it doesn't just potentially affect Rodgers' preparation and sharpness, but that of the entire team.

In turn, a lot of responsibility for the tempo and energy at practice falls on backup QBs DeShone Kizer and Tim Boyle, but by the same token, there's only one Aaron Rodgers.

"Anytime your quarterback doesn't practice, it's different," McCarthy said. "Aaron Rodgers brings a tremendous amount – forget about the game plan or scheme you're running that week – but the competitive nature.

"When you feel the quarterback on the field, that's huge, as far as his cadence, his presence, the competition, it's such a big part. Those are things that don't show up in the scouting report or you see on video.

"He's clearly the guy who stirs the drink down there on Hinkle Field, and the quarterback position has to bring that to your program. You can't grow during the week if your quarterback doesn't bring that. We had it with Brett and we have it with Aaron."