With a short week and what he sees as a very difficult road game Sunday at Buffalo — a place where the Packers have never won in five tries — McCarthy made it clear he was moving on Tuesday.
He fielded several questions about the defense, which gave up 30 points and 304 yards after the Packers took a 31-7 lead into halftime.
"I'm not going to sit here and talk about defense all day," McCarthy said tersely. "We're on to Buffalo."
The Packers' biggest problem against the Falcons was their inability to defend wide receiver Julio Jones, who caught 11 passes for 259 yards — the most an opposing receiver has ever amassed against Green Bay — before leaving the game with a hip injury.
Cornerback Sam Shields, re-signed by the Packers to a four-year, $39 million deal in March, struggled in coverage against Jones after leaving the Nov. 30 game against New England with a concussion sustained on the 10th defensive snap.
Shields missed practice last week on Thursday and Friday and was listed as questionable for Monday's game.
McCarthy went out of his way to support Shields on Tuesday.
"He's our guy," McCarthy said after the coaches replaced him in the second half with backup Davon House.
McCarthy said House's insertion into the lineup was part of a pre-planned "rotation," although Shields never went back into the game.
"Hey, they had a big day. Julio had a huge night. They got hot in the second half," McCarthy said. "We'll have time to correct our things (Wednesday) with our players, and we'll learn from it. Obviously, you always want to make corrections after a win."
The Packers (10-3) have won five in a row and are tied for the best record in the NFL. They are 7-0 at home and are aiming for the NFC's No. 1 seed to have the road to the Super Bowl go through Lambeau Field.
Players were off Tuesday, but quarterback Aaron Rodgers said during his weekly show on 540 ESPN radio in Milwaukee that he likes where his team stands with three weeks to go in the regular season.
"This is when it gets exciting. It's right in front of us," said Rodgers, who has led the Packers to an NFL-best 423 points. "We have the opportunity to achieve the goals that we talk about every season, and the first and most important is winning your division and getting a home playoff game.
"That's right in front of us. We control our fate right there and we have the opportunity to do some great things. But we have to take care of business."