GREEN BAY, Wis. -- The bigger the game, the more the little things matter.

That's how Green Bay Packers defensive coordinator Dom Capers is approaching the preparation for Sunday's game against Tom Brady and the New England Patriots (9-2) at Lambeau Field.

"Well, you have to be sharp," Capers said Monday. "There's not a lot of margin for error when you're going against a quarterback that's done it for as long as he's done it with the level of efficiency he's done it with. There's not many things he hasn't seen."

For a good portion of Monday's group session with reporters, Capers used words like "sharp" and phrases such as being "on top of your game" when talking about the Patriots.

When asked later what he meant by those, Capers pointed to three instances from Sunday's 24-21 win at the Minnesota Vikings that, if repeated against the Patriots, could prove more costly.

They were:

On a fourth-and-5 play in the second quarter, Morgan Burnett's interception was wiped out because of a holding penalty on Micah Hyde. The Vikings scored their first touchdown on that drive.

On a third-and-6 play in the second quarter, Hyde had a chance to tackle running back Joe Banyard short of the line to gain but instead Banyard carried him for 3 extra yards and a first down. (Hyde made up for it with an interception on the next play.)

On a third-and-4 play in the fourth quarter, outside linebacker Mike Neal was flagged for a neutral-zone infraction, which gave the Vikings a first down and led to the touchdown that pulled them to within three points with 3:23 left in the game.

"Those are the kind of things that in a game like this, these guys are efficient enough, you can't give them any advantage with, say, penalty-aided drives." Capers said. "Both of the [Vikings'] touchdown drives yesterday were penalty-aided."

The Vikings did not have the experienced quarterback or the playmakers to make Capers' defense pay for its mistakes.

The Patriots (9-3) do with Brady and his supporting cast of tight end Rob Gronkowski -- a match-up nightmare for linebackers and safeties alike -- receiver Julian Edelman and whichever running back they decide to use on a particular week. Two games ago, it was Jonas Gray, who rushed for 201 yards. The last game, it was the recently re-signed LeGarrette Blount, who had two touchdowns in his return to New England.

"We certainly have probably the biggest challenge coming in here Sunday," Capers said. "We've got to go back to work and make sure we're on top of our game and we're ready to go out and play our best, because that's what it's going to take to win a game like this."

When it was posed to coach Mike McCarthy on Monday that the Packers (8-3) would need to be sharp against Brady and Co., he replied: "So you're saying we're not sharp?"

Then how about extra sharp?

"OK, well extra sharp will be the focus," McCarthy said. "You gave me my theme for the week, I guess, there."

And then his tone turned more serious.

"New England is a great football team," McCarthy said. "Just the way they're hitting their stride right now, just watching the video this morning, very impressive. We'll stay in tune with that. We're not going to make a bunch of changes. We like the football team that we are, and we look forward to the competition."