With starting quarterback Aaron Rodgers set to miss his second straight game with a fractured left collarbone, McCarthy's focus Monday in the wake of the team's second straight loss wasn't on new starter Scott Tolzien, who played well against Philadelphia on Sunday after veteran backup Seneca Wallace suffered a groin injury on the opening series.
Rather, McCarthy's concern is with his defense, which allowed Eagles running back LeSean McCoy to run for 155 yards and had quarterback Nick Foles throw 55-, 45- and 32-yard touchdown passes in the Eagles' 27-13 victory at Lambeau Field.
McCarthy was also unhappy that for the second straight week, his defense couldn't stop the opponent in the fourth quarter.
A week ago against Chicago, the defense allowed the Bears to drive 80 yards in 18 plays and use 8 minutes, 58 seconds in the fourth quarter. By the time kicker Robbie Gould made a field goal to push Chicago's lead to 27-20, the Packers had used all three of their timeouts and only 50 seconds remained in the game.
On Sunday, after Tolzien's fourth-down pass to Jordy Nelson in the end zone was ruled incomplete and the call withstood McCarthy's replay challenge, the Eagles took over with 9:32 to play and kept the ball the rest of the game.
"What I'm disappointed in, and it's gone on all year, is our fourth-quarter performance. We're not playing our best football when it counts," McCarthy said Monday.
"We don't have a drill for (fixing) it, particularly on Mondays, but it's something we've been emphasizing. And to see it happen again (Sunday) is obviously disappointing and frustrating."
Defensive coordinator Dom Capers, whose group has just three interceptions this season after picking off more passes over the past four seasons (103) than any team in the NFL.
The Packers had at least two opportunities for interceptions Sunday. On one, the ball caromed off cornerback Tramon Williams' shoulder and helmet and into the arms of Eagles wide receiver DeSean Jackson for the 55-yard touchdown; the other went through the hands of a leaping Williams for a 23-yard completion to Jason Avant.
The Packers' takeaway came on a sack of Foles by Williams and defensive tackle Mike Daniels in the fourth quarter. The turnover failed to lead to points when Nelson's near-catch was incomplete.
"Those are the kind of plays you want to make. Those are game-changing plays," Capers said of the fumble.
"Obviously the most disappointing thing was they hit three balls over the top on us for touchdowns. Those are things you've got to get rectified because no matter what else you do in the game, if you give up touchdowns over the top, it's going to be hard to overcome."
Meanwhile, McCarthy confirmed that Rodgers will miss back-to-back games for the first time in his career and won't play Sunday against the Giants.
"He thinks he'll be ready to go real soon," McCarthy said. "But he's a couple weeks away I would think."
In his place, the Packers will go with Tolzien, who'd never thrown a regular-season NFL pass before Sunday.
With Rodgers and Wallace out, McCarthy confirmed that former No. 2 quarterback Matt Flynn worked out for the team Monday, but he wouldn't say if Flynn would be signed to back up Tolzien.
"Matt Flynn is here," McCarthy said Monday afternoon. "(He) went through his workout this morning. (He) looks good. That's really all I have for you right now. Everything else is a work in progress."
Asked how much the offense has changed since Flynn threw for 480 yards and six touchdowns for the Packers in the 2011 regular-season finale against Detroit, offensive coordinator Tom Clements said on Monday afternoon: "It's still the same the terminology and the same basic plays."
McCarthy also had no update on the injuries sustained by starting center Evan Dietrich-Smith (knee), starting right tackle Don Barclay (knee), starting defensive end Johnny Jolly (groin), starting outside linebacker Nick Perry (foot) or No. 3 cornerback Casey Hayward (hamstring), all of whom left Sunday's game with injuries.