That self-assurance will be tested Sunday, when his injury-riddled offense could start three rookies in the season opener against Philadelphia at Lambeau Field.
Jennings didn't practice Friday after injuring a hamstring a day earlier.
"We're just being smart with him today," McCarthy said after practice Friday. "He feels good about Sunday's contest. But, we'll work him again tomorrow."
Jones, a third-round draft pick, led Green Bay in the preseason with 21 catches for 233 yards and two touchdowns.
Top receiver Donald Driver had full participation in a practice for the first time this week and is probable for the game.
Driver suffered a sprained foot in the Aug. 23 preseason game against Jacksonville and missed the final exhibition contest.
"I thought Donald looked good. I don't foresee him having a problem, if he does go," McCarthy said.
The biggest mystery for the Packers going into the start of the season is their running game. The halfback position has been unsettled since the first day of training camp, when projected starter Vernand Morency injured a knee.
Morency returned to practice this week but was held out Friday and is questionable on the injury report.
"He's sore," McCarthy said. "As far as where he is in his rehab, (team doctor Pat) McKenzie is looking for a little better recovery the next day when he really does push it. We did some things with him today, and we'll see how he feels tomorrow."
Morency's injury opened the door for Jackson, a second-round draft pick, to assume the role of featured back in the preseason.
Jackson suffered a concussion in practice last week, which kept him out of the preseason finale, but he has been cleared to play Sunday.
McCarthy feels Jackson is capable of carrying a full load in his pro debut.
"He's definitely young enough and strong enough. He's built for that," McCarthy said. "I don't think he's a guy you have to keep it at 10 to 15 (carries). I think he's definitely physical enough to go 20 to 25."
Rookie DeShawn Wynn and Ryan Grant would spell Jackson if Morency is kept out Sunday.
Notes: DE Aaron Kampman was added to the injury report because of a rib injury he suffered in practice Thursday. Kampman had limited participation Friday but is probable. ... DE Michael Montgomery (knee) has been declared out. ... OT Tony Moll (neck) and S Aaron Rouse (hamstring) are doubtful.
Copyright 2007 by The Associated Press