As sure as the sun wants to rise in the morning and the leaves want to flitter to the ground once the mid-October chill arrives, McCarthy wants to run the football. It's in his DNA, not to mention tattooed on the inside of his eyelids and printed in block letters on the welcome mat outside his house.
But, as the Packers have pounded home with the repetitiveness of the last few minutes of Journey's "Lovin', Touchin', Squeezin'" (na na na na na na), they couldn't run the ball successfully if they were facing the Baylor Bears instead of the Chicago Bears.
This roster, at least for this season, is built to pass the ball. A fact that gained a few exclamation marks with the reinstatement of receiver Koren Robinson, the injury that sidelined run-blocking tight end Bubba Franks and the latest boo-boo that has starting halfback DeShawn Wynn's status for this week in jeopardy.
With all of that, is there any doubt McCarthy's plan of attack for Monday's game at Denver will be pass, pass and pass some more?
Of course not. The one time McCarthy stuck with the running game, against Chicago, his stick-to-it-iveness played at least a small role in the Packers dropping their only game of the season.
The crossroads, however, could come Monday at Denver. Or the following week at Kansas City. Seven of the Packers' final 10 games have the potential of being played in inclement weather, including December games at home against Oakland, at Chicago and home to Detroit.
Not that it's impossible to throw the ball when the weather outside is frightful, but it's not exactly a recipe for success. Recall a few of those mid-1990s games, when Edgar Bennett was just as important as NFL MVP Brett Favre. Or, for more recent history, recall what happened during last December's three home games.
During a 38-10 loss to the New York Jets on Dec. 3, when it was breezy and 19, Favre completed 24 of 47 passes for 214 yards with one touchdown and two interceptions.
During a 17-9 victory over Detroit on Dec. 17, played when it was 41 but pleasant, Favre completed 20 of 37 passes for 174 yards, with no touchdowns, three interceptions and a passer rating of 32.9.
During a 9-7 victory over Minnesota on Dec. 21, played when it was 36 and rainy, Favre completed 26 of 50 passes for 285 yards, with no touchdowns, two interceptions (one of which was returned for the Vikings' only points) and a passer rating of 52.5.
While the receiver, with the advantage of knowing his route, can take advantage of a slippery field, that edge is outweighed by the messed-up timing between quarterback and receiver, not to mention the ball being harder to throw and catch.
Beyond the weather, the Packers need a running game to drain the clock. That's something they failed to do in wins against Minnesota and Washington, but that failure could come back to bite them against a quality team.
That combination of factors poses quit the dilemma for McCarthy, and it's something he no doubt spent a few minutes pondering during the bye.
Do you just chuck the chapter titled "Run Plays" from the playbook, and pass it 80 percent of the time and hope Mother Nature is shining on you? Or, do you keep plugging away at the running game, knowing doing so could take the steam out of an effective passing game, not to mention be a waste of precious practice time?
It's a tough question for McCarthy. The fate of the season rests with his answer.
Steve Lawrence is a regular contributor to PackerReport.com. E-mail him at firstname.lastname@example.org