But key players such as quarterback Aaron Rodgers aren't expected to be on the field long when the Packers host the Arizona Cardinals on Friday night.
"Our No. 1s will definitely start the game," McCarthy said after practice Thursday.
Green Bay already is undermanned for the game with several top contributors out with injuries.
Among those who won't play are receiver Jordy Nelson, left tackle Bryan Bulaga and cornerback Tramon Williams. All three players have significant knee injuries, and Bulaga will likely miss the entire season after he undergoes surgery for a torn ligament next week.
The attrition at several positions two weeks into training camp has given the Packers plenty of opportunities to put the "next man up" theory to the test.
"I don't think we've ever really said, 'Here we go again,'" Rodgers said about the rash of injuries. "We believe in the next guy up. We've seen a lot of that — a guy getting an opportunity and making the most of it and emerging as a big-time contributor. That's the expectation around here. That's why we like to have a lot of depth."
The Packers' recent injury woes on the offensive line and how they are going about plugging holes is one example.
Rookie David Bakhtiari, a fourth-round draft pick, has been thrust into a critical starting role as the replacement for Bulaga to protect Rodgers' back side. McCarthy indicated Bakhtiari would play longer than some of the other starters Friday with an eye on getting the newcomer settled at the spot.
"David needs to play," McCarthy said. "He needs to learn to play the position at this level and speed and see the things he's going to see in Week 1."
The Packers had only nine offensive linemen in practice Thursday. Right guard T.J. Lang was held out with a sore back, and McCarthy wasn't sure whether Lang would be available for the game.
McCarthy said he hopes to play all four quarterbacks, including newly signed veteran Vince Young, in Friday's game. Young last played in the 2012 preseason with the Buffalo Bills. After practicing the last three days, Young said he would be ready to play against Arizona.
"I had an opportunity to play a lot of games in the NFL," Young said. "So I feel like that's the help part that's kind of making me feel that if I do go in and play I will be comfortable. I just want to make sure I've got the right plays, and I want to make sure I get the guys out of the huddle."
With Nelson out and the playing status of fellow injured playmaker Randall Cobb up in the air, several young receivers will get their chance to make a good first impression Friday.
Cobb is nursing a biceps injury and said he is prepared to play against the Cardinals if he's given the OK. If not, the third-year player knows how important playing time and playing well in the preseason is for young prospects trying to make the team.
"When the lights come on, some guys shine, some guys kind of fall under," he said. "Practice is one thing, and we've had some guys doing really well in practice. But once the lights come on, it's going to be really the test for them."
James Jones, who could be the only veteran receiver in uniform for the Packers as they welcome first-year coach Bruce Arians and the Cardinals to Lambeau Field, is looking forward to seeing the likes of young receivers Jarrett Boykin and Jeremy Ross get an extended look.
"I'm excited to see them get an opportunity to make plays, to go out there and put some good film on tape, to finally see some new faces and play against some other people," Jones said.
The offense also might be without rookie running back Eddie Lacy, who ran the football well in a scrimmage Saturday. Lacy, a second-round draft pick, has been bothered by a hamstring injury and didn't practice the last two days.
As for Green Bay's defense, which will see a new-look Arizona offense with veteran additions Carson Palmer at quarterback and Rashard Mendenhall at running back, Williams is out indefinitely with the knee injury he sustained July 28.